Process for preparing an algal powder containing a reduced content of proteins, and bioplastic composition formulated from such a powder

Abstract

A process for preparing an algal powder containing a reduced content of proteins, a bioplastic composition formed from such a powder, a process for manufacturing a plastic product obtained from such an algal powder and also the plastic product obtained in this way. Process for preparing an algal powder, especially intended for the manufacture of a plastic product, including the successive steps of: culturing and/or harvesting an algal biomass; reducing by at least 10% the intrinsic amount of proteins of the algae, by weight relative to the weight of proteins of the harvested biomass; drying; and reducing to give powder or granules.

Claims

1. A process for preparing an algal powder, comprising the successive steps of: (a) harvesting algae; (b) culturing the algae in conditions favoring the biosynthesis of starch, said culturing comprising setting up the algae in a tank and culturing for four to six weeks in a seawater culture medium without supplying fertilizers, and without supplying nitrogen; (c) depigmenting the algae in the presence of ethanol; (d) reducing by at least 75% the amount of intrinsic proteins of the depigmented algae by enzymatic hydrolysis of the intrinsic proteins, the reducing step (d) comprising: (d1) macerating over night the depigmented algae in water, filtering the macerated algae to generate a first algal residue, and recovery of the first algal residue, (d2) mixing the recovered first algae residue with a sodium hydroxide solution to produce a mixed algae, filtering the mixed algae to generate a second algal residue, and recovery of the second algal residue, (d3) mixing the recovered second algae residue and Bacillus licheniformis as a source of one or more proteases to hydrolyze the intrinsic proteins, then (d4) separating a hydrolysate enriched in peptides and/or amino acids from the hydrolyzed second algal residue to generate a third algal residue, and recovery of the third algae residue; (e) destructuring the cell walls of the recovered third algal residue by mixing the third algae residue with a chelating agent and water, heating the mixture to a temperature of between 80 C. and 100 C., to generate a fourth algal residue, then cooling and concentrating the fourth algal residue by elimination of water; (f) adding starch to the concentrated fourth algal residue to form a dispersion of the starch and the concentrated fourth algal residue, (g) drying an algal material derived from the dispersion, and (h) reducing the dried material of the step (g) to give powder or granules, thereby obtaining the algal powder.

2. The process according to claim 1, further comprising adjusting the pH of the concentrated fourth algal residue before adding the starch to the concentrated fourth algal residue; mixing the dispersion of the starch and the concentrated fourth algal residue generated in the step (f); heating the mixed dispersion to a temperature of between 80 C. and 100 C. for 1 to 3 hours; cooling to a temperature of between 45 C. and 50 C., thereby providing the algal material derived from the dispersion.

3. The process according to claim 1, wherein the algae are microalgae or macroalgae.

4. The process according to claim 1, wherein the chelating agent is citric acid.

5. The process for preparing an algal powder according to claim 1, wherein said step of destructuring the cell walls further comprises a step of adjusting the pH of the mixture of the third algae residue, the chelating agent, and water to a pH between 2.5 and 3.5 before the mixture is subjected to the heating, wherein the mixture is heated at a temperature between 80 C. and 100 C. for 1 to 4 hours, and then cooled to a temperature less than or equal to 45 C.; and a step of neutralizing the pH of the concentrated fourth algal residue to between 7 and 8 by means of a base, before the starch is added to the concentrated fourth algal residue.

6. The process according to claim 5, wherein the base is sodium hydroxide.

7. A process for manufacturing a plastic product, comprising the steps (a)-(h) for preparing an algal powder, as described in claim 1, and further steps of preparing a bioplastic composition from the algal powder, and extruding said composition to generate granules.

8. The process for manufacturing a plastic product according to claim 7, further comprising a step of forming the plastic product by injection moulding, extrusion blow moulding, or sheet die extrusion of said bioplastic composition.

Description

EXAMPLE 1: OBTAINING A CONTROL ALGAL POWDER

(1) Green algae of the species Ulva Armoricana were harvested, dried to give flakes at 50 C., then reduced to particles with a mean size of 100 m in diameter. 2 kg of powder was thus obtained. The composition of the algal powder is given in table 1.

(2) TABLE-US-00001 TABLE 1 Dry matter (DM) 88.9% dry Starch content 4.1% dry/crude* Protein content 14.5% dry/crude *% dry/crude: Weight of dry matter of the compound relative to the weight of crude dried algae, that is to say without correcting for the percentage of residual moisture still remaining in the dried algae.

(3) It is noted that the starch content is 4.1% dry/crude in this powder.

EXAMPLE 2: OBTAINING AN ACTIVATED CONTROL ALGAL POWDER ENRICHED IN STARCH

(4) The process used carried out the following steps in the following order, described in detail in the following example 3:

(5) 1harvesting a biomass of Ulva Armoricana green algae, and enrichment under conditions promoting starch synthesis,

(6) 2depigmentation,

(7) 3absent (step of reduction of the intrinsic content of proteins not carried out),

(8) 4destructuring the cell walls by treatment with citric acid (step of activation of the algae),

(9) 5addition of starch (final mixture of 60% dry weight of activated algae and 40% dry weight of starch),

(10) 6precipitation/filtration,

(11) 7drying/reducing to give powder with a mean size of 100 m in diameter.

(12) Steps 1, 2, 4, 5 and 6 will therefore occur like those of the following example 3.

EXAMPLE 3: OBTAINING AN ACTIVATED ALGAL POWDER ACCORDING TO THE INVENTION, DEPROTEINIZED AND ENRICHED IN STARCH

(13) The process used carried out the following steps in the following order, expanded upon below:

(14) 1harvesting a biomass of Ulva Armoricana green algae, and culturing under conditions promoting starch synthesis,

(15) 2depigmentation,

(16) 3reducing the intrinsic content of proteins,

(17) 4destructuring the cell walls by treatment with citric acid (step of activation of the algae),

(18) 5adding starch,

(19) 6precipitation/separation,

(20) 7drying and reducing to give powder with a mean size of 100 m in diameter.

(21) 1. Harvesting and Culturing Biomass Under Conditions for Enrichment in Starch:

(22) Ulvas, of the species Ulva Armoricana were harvested in France over a period across September and October. During such a period, they have high initial contents of glucose which favour endogenous enrichment in starch. The algae were cultured for 1 month and 4 days in a tank and under nitrogen-deprived conditions. The light conditions were based on the natural light in the months of October and November in Brittany (France). An amount of 18 kg of fresh material was obtained. The algae harvested were frozen under vacuum, without rinsing in freshwater.

(23) 15 kg of fresh algae were subsequently defrosted and ground using an URSCHEL-type mill, over a 66896 screen. After defrosting and grinding, 14.65 kg of ground algae were obtained. The following data were measured:

(24) Content of dry matter: 21.38%

(25) Weight of algae (DM: dry matter): 3.13 kg

(26) Protein content: 9.29% dry/dry, i.e. 0.29 kg of proteins

(27) Glucose content (starch): 32.80% dry/dry

(28) The glucose content is representative of the starch content, since the starch is converted into glucose during the quantitative and qualitative analyses. It is noted that the glucose content is 32.80% dry/dry, compared to the glucose content of example 1, of 4.1% dry/crude. There was indeed therefore stimulation and increase in the synthesis of starch by the alga during a culture thereof under conditions favourable to the synthesis of starch by the alga.

(29) 2. Depigmentation with Ethanol:

(30) After grinding, carrying out four successive aqueous-ethanolic macerations with the aim of removing as much chlorophyll as possible and of bleaching the alga. Each maceration is carried out by soaking the ground algae for 1 to 3 days in the presence of 25 l of ethanol. At the end of these maceration steps, the mixture is filtered over a cloth having 100 micron diameter pores, and the ground and depigmented algae are recovered. The amount of bleached ulvas obtained is 14.90 kg having a DM of 16.47%, i.e. 2.45 kg dry. The yield by weight of this step is 78%.

(31) The total protein content is determined by the Kjeldhal method (N6.25). The principle of this method is a multiplication of the inorganic nitrogen content by a mean coefficient which represents the nitrogen richness of the animal or plant proteins. The total protein content is expressed as percentage of proteins (weight of dry matter) relative to the dry weight of the crude dried depigmented ulvas, that is to say without correcting for the few percentages of moisture present in the dried alga.

(32) Summary:

(33) Amount of dry matter of the algae at the start of the step: 3.13 kg

(34) Amount of dry matter of the algae at the end of the step: 2.45 kg

(35) Protein content: 10.4% dry/crude, i.e. 0.25 kg of proteins

(36) Starch content: 32.1% dry/crude

(37) 3. Reducing the Intrinsic Content of Proteins:

(38) The aim of this step is to hydrolyse the proteins enzymatically and to extract the hydrolysates in basic medium. 13.65 kg of depigmented ulvas were used (DM content of 16.47%), i.e. 2.24 kg dry.

(39) 3.1 Aqueous Maceration

(40) Suspension of 13.65 kg of depigmented ulvas resulting from the previous step, i.e. 2.24 kg dry, in 47.8 kg of demineralized water and stirring with Rayneri turbine for 30 minutes (DM 3.57%). Then, addition of 11.68 kg of demineralized water to obtain 3.02% DM.

(41) Maceration overnight at a temperature of 7 C., then static separation over 100 m sieve. In a second stage, manual pressing of the algal residue remaining on the 100 m sieve with a 30 m cloth.

(42) Summary of this sub-step: amount: 57 kg (DM: 0.47%) of filtrate and 14.8 kg (DM: 13.04%) i.e. 1.92 kg dry of algal residue. The intermediate yield by weight of this step is 85%.

(43) 3.2. First Extraction with Sodium Hydroxide:

(44) This step promotes extraction and accessibility to the enzyme. It enables the extraction of soluble proteins in order to promote the action of the enzyme specifically on insoluble proteins.

(45) The residue resulting from sub-step 3.1 is taken up (1.92 kg dry) in demineralized water and suspended at 3.5% DM. Next, addition of 30% sodium hydroxide, in a sufficient amount to give a final solution with a concentration of 0.12 M.

(46) Stirring with Rayneri turbine for 1 h 30.

(47) Static separation over 100 m sieve (drip-draining overnight at room temperature), then manual pressing of the algal residue remaining on the 100 m sieve with a 30 m cloth.

(48) Summary of this sub-step: amount: 40.2 kg (DM: 1.04%) of filtrate and 14.7 kg (DM: 12.68%) i.e. 1.86 kg dry of algal residue. The intermediate yield by weight of this step is 96%.

(49) 3.3. Enzymatic Hydrolysis with an Alcalase Protease:

(50) Taking up the algal residue from sub-step 3.2 (1.86 kg dry) in demineralized water for suspension at 3.5% DM, i.e. 47.43 kg of demineralized water. Transfer of the medium into a round-bottomed concentrating vessel then adjustment of the pH to 8.0 with 140 g of 96% sulfuric acid (starting pH 12.3). Stirring using a stirrer at maximum speed, and heating to 55 C. Once at temperature, addition of 3.28 g of Alcalase enzyme from Novozymes, a protease derived from Bacillus lichenformis (Sigma ref: P4860, 2.4 U/g). Generally, the enzyme is added at a concentration of between 0.1 and 10% relative to the dry weight of proteins, preferentially between 0.8 and 3%, more preferentially between 1 and 2%. Stirring overnight (12 h) at 55 C.

(51) 3.4. Second Extraction with Sodium Hydroxide:

(52) After cooling to 30 C., adjustment of the pH to 12.0 with 498 g of 30% NaOH (initial pH: 5.23). Static separation over 100 m sieve then, in a second stage, manual pressing of the algal residues remaining on the 100 m sieve with a 30 m cloth.

(53) Summary of this step: amount: 47 kg (DM: 1.97%) of filtrate and 14 kg (DM: 8.90%) i.e. 1.24 kg dry of algal residue. The intermediate yield by weight at this step is 66%.

(54) The filtrate, rich in protein matter (peptides and amino acids), is harvested with a view to subsequent exploitation.

(55) 3.5. Rinsing the Algal Residue in Water

(56) Taking up the residue obtained in sub-step 3.4 (1.24 kg dry) and rinsing with demineralized water for suspension at 3% DM, i.e. 27.53 kg of demineralized water added.

(57) Stirring for one hour and separation over 100 m sieve overnight (no pressing with 30 m cloth required).

(58) Summary:

(59) Amount of dry matter of the algae at the start of the step: 2.24 kg

(60) Amount of dry matter of the algae at the end of the step: 1.11 kg

(61) Yield by weight: 49%.

(62) Protein content: 5.6% dry/crude, i.e. 0.06 kg of proteins

(63) Starch content: 49.4% dry/crude

(64) The protein content of the algal residue, determined by the Kjeldhal method (N6.25) is 5.6% dry/crude. The protein content in the residue (5.6% dry/crude) has been reduced by 46% relative to the protein content in the residue from the previous step (10.4% dry/crude).

(65) The final amount of proteins (0.06 kg) has been reduced by 79% by weight, relative to the total starting protein amount (0.29 kg).

(66) Enzymatic Hydrolysis Using Another Enzyme:

(67) Enzymatic hydrolysis of the proteins was carried out, by way of comparison, on 2 kg of biomass in order to check the feasability of the process using other proteases, especially using a protease derived from Aspergillus oryzae and sold under the name Flavourzyme by Sigma. The algal biomass used in this test underwent the same steps as steps 1 to 3 described above. The protein content was reduced by 12% (amount of residual proteins (by weight), relative to the amount of proteins initially present). The colour characteristics are the obtaining of a yellow-green residue like in the case of the use of Alcalase. However, a relatively unsatisfactory odour is noted. Hydrolysis using Alcalase is preferred.

(68) 4. Activation of the Algae: Destructuring of the Cell Walls:

(69) As a reminder, the principle is that of destructuring the cell walls by means of a polysaccharide-solubilizing agent, in the present case using a chelating agent, and more specifically that of breaking the bonds, especially the ionic bonds, involving the cell wall polysaccharides, in order to make the cell wall polysaccharides accessible, free, and functional, hence active, without being obliged to extract them by means of precise and refined extraction processes. At the end of this step, the algal residue recovered contains polysaccharides and also all the non-polysaccharide components present before carrying out this step.

(70) The algal residue resulting from step 3 is taken up to be ground in a colloid mill tightened as much as possible in order to have a smooth paste, with addition of 12 kg of water in order to propel the residues and rinse the mill. After grinding, obtaining 26.6 kg (DM: 4.07%) of an algal residue in the form of a thick puree, i.e. 1.08 kg dry.

(71) Transfer of the ground algal residue, i.e 26.6 kg, into a 100 l enameled reactor and addition of 11.4 kg of water to rinse the equipment. In total, 38 kg of ground material (final calculated DM: 2.85%), i.e. 1.08 kg dry, employed for activation by means of a chelating agent: citric acid monohydrate.

(72) The pH is adjusted to 3 with 436.5 g of citric acid monohydrate.

(73) The reaction medium is heated and kept at 90 C. for 2 hours with stirring, then cooled to room temperature (measurement of the pH after cooling: 3.06).

(74) Then, all the medium (algal residue and liquid) is transferred directly into a round-bottomed concentrating vessel and concentrated under vacuum at 45 to 50 C. Approximately 15 litres of water are then eliminated. At this stage, the absence of a separation or filtration step, leading to the elimination of non-polysaccharide compounds, is noted.

(75) 22.2 kg, at 6.31% DM, i.e. 1.4 kg dry, of concentrate are recovered.

(76) Neutralization of the concentrate to pH 7.7 with 510 ml of 30% NaOH (DM after neutralization: 6.78%), i.e. 1.5 kg dry.

(77) The intermediate yield regarding this overall activation step is considered to be 100% since no source of loss is identified (1.08 kg+0.487 kg of sodium citrate).

(78) Summary:

(79) Amount of dry matter of the algae at the start of the step: 1.11 kg

(80) Amount of dry matter of the algae at the end of the step: 1.54 kg

(81) Protein content: 4% dry/crude

(82) Starch content: 34.4% dry/crude

(83) 5Addition of a Dispersion of Starch

(84) The concentrate of activated algae resulting from the previous step is used at an amount of 22.2 kg (6.78%), i.e. 1.5 kg dry.

(85) A dispersion of starch was prepared so as to obtain a final mixture of 60% by dry weight of activated algae and 40% by dry weight of starch. In order to avoid adding too much water, preparation of a dispersion at approximately 10% starch, i.e. 8.29 kg of water and 1.01 kg of starch. The dispersion of starch is kept at 90 C. for 30 minutes (cooking). The dispersion is highly viscous; 10% is a limit which it is preferable not to exceed.

(86) Transfer of the concentrate of activated algae and of the dispersion of starch at 90 C. into a container enabling stirring using the Rayneri device. Stirring for three hours for thorough mixing, then transfer of the 34 kg of dispersion into 102 l of alcohol (80 l of fresh alcohol and 22 l of recycled 90 alcohol).

(87) Mixing then resting the solution overnight for settling out. Separation of the precipitate over a 30 m cloth, then manual pressing over a 20 m cloth. The amount of pressed mixture recovered is 13.1 kg.

(88) Drying in the oven, heating for 5 h at 45 C. The yield of this step is 152%.

(89) Summary:

(90) Amount of dry matter of the algae at the start of the step: 1.5 kg

(91) Amount of dry matter of the algae at the end of the step: 2.3 kg

(92) Protein content: 2.4% dry/crude, i.e. 0.05 kg of proteins

(93) Starch content: 53.4% dry/crude

(94) 6. Grinding:

(95) First grinding using Forplex pins takes place, followed by a second grinding on 100 m Forplex screen.

(96) Amount after grinding: 1.91 kg.

(97) Grinding yield: 83% by weight, associated with the dead volumes of the mills.

(98) The particle size distribution of these ground algae is as follows:

(99) TABLE-US-00002 >250 m 0% 250 m-160 m 0.48% 160 m-80 m .sup.20% 80 m-40 m 75.23% <40 m 4.29%

(100) It is noted that, at the end of the process, an algal powder containing 2.4% of proteins and 53% of starch, as percentage of dry weight relative to the total dry weight of the powder, is obtained.

EXAMPLE 4: BIOPLASTIC COMPOSITIONS

(101) Bioplastic compositions were formulated by mixing the algal powders of examples 1, 2 and 3 with other compounds. Native corn starch is used as control. The compositions formulated are extruded in the form of granules. A total of 49 compositions were formulated. Table 2 below indicates the compositions of the mixtures produced:

(102) TABLE-US-00003 TABLE 2 Type of powder Formulation Starch Plasticizer Polymer No. (control) (example 1) (example 2) (example 3) Diglycerol PBAT 1 35% 5% 60% 2 45% 7% 48% 3 55% 8% 37% 4 25% 4% 71% 5 35% 5% 60% 6 45% 7% 48% 7 55% 8% 37% 16 25% 4% 71% 17 35% 5% 60% 18 45% 7% 48% 19 55% 8% 37% 34 25% 4% 71% 35 35% 5% 60% 36 45% 7% 48% 37 55% 8% 37% Continuation: Type of powder Plasticizer Polymer Formulation Starch Example 1 Example 2 Example 3 Diglycerol PPC 8 25% 4% 71% 9 35% 5% 60% 10 45% 7% 48% 11 55% 8% 37% 22 25% 4% 71% 23 35% 5% 60% 24 45% 7% 48% 25 55% 8% 37% 40 25% 4% 71% 41 35% 5% 60% 42 45% 7% 48% 43 55% 8% 37% Continuation Type of powder Plasticizer Polymer Formulation Starch Example 1 Example 2 Example 3 Diglycerol PBS 12 25% 4% 71% 13 35% 5% 60% 14 45% 7% 48% 15 55% 8% 37% 28 25% 4% 71% 29 35% 5% 60% 30 45% 7% 48% 31 55% 8% 37% 46 25% 4% 71% 47 35% 5% 60% 48 45% 7% 48% 49 55% 8% 37% PBAT: (polybutylene adipate terephthalate) PPC: Polypropylene copolymer PBS: Polybutylene succinate

(103) Formulations 34 to 37, 40 to 43 and 46 to 49 comprise between 25 and 55% by weight relative to the total weight of the compositions of an algal powder obtained according to example 3. These are algae in which the protein content has been reduced, the intrinsic amount of starch has been increased, a supply of starch has been added and the cell wall polysaccharides have been made functional.

EXAMPLE 5: EXTRUSION IN THE FORM OF GRANULES OF THE COMPOSITIONS OF EXAMPLE 4

(104) The extrusion conditions are indicated in table 3

(105) TABLE-US-00004 TABLE 3 Formulation Extrusion conditions Injection 1-3 160, 170, 180 C. - 100 rpm 170 C. - 8 bar 4-7 140, 170, 180 C. - 100 rpm 170 C. - 8 bar 8-10 140, 170, 180 C. - 50 rpm 170 C. - 8 bar 12-15 120, 140, 160 C. - 75 rpm 160 C. - 8 bar 11 140, 190, 200 C. - 50 rpm: 180 C. - 8 bar extrusion difficult 16 120, 140, 160 C. - 50 rpm 160 C. - 8 bar 17 120, 140, 170 C. - 50 rpm 170 C. - 8 bar 18 120, 160, 180 C. - 50 rpm 180 C. - 8 bar 19 130, 160, 180 C. - 50 rpm: 180 C. - 8 bar extrusion difficult 22-25 140, 170, 180 C. - 50 rpm 170 C. - 8 bar 34-37 120, 140, 170 C. - 50 rpm 170 C. - 8 bar 40-42 140, 170, 190 C. - 50 rpm 180 C. - 8 bar 43 Extrusion impossible

(106) The characteristics of odour, of colour and the mechanical characteristics of the extruded compositions are presented in table 4:

(107) TABLE-US-00005 TABLE 4 Mechanical properties Number Breaking of test Modulus, Threshold Threshold strength Breaking Formulation Odour Colour specimens MPa stress strain MPa strain % 1 bread Light beige 5 99 (3) 10.4 (0.1) 31.9 (1.5) 15.6 (1.2) 387 (225) 2 bread beige 3 143 (2) 9.9 (0.7) 18 (2) 12.1 (1.4) 269 (67) 3 bread beige 5 167 (9) 10.5 (0.1) 14.3 (0.5) 11.7 (0.5) 186 (35) 4 Algae Dusky brown 3 83 (3) 11.8 (0.2) 46.4 (2) 21 (0.3) 477 (10) 5 Algae Dusky brown 4 100 (2) 11.7 (0.1) 41.4 (1) 18.4 (0.5) 458 (27) 6 Algae Dusky brown 5 124 (13) 11 (0.2) 36.5 (4) 13.2 (0.5) 266 (23) 7 Algae Dusky brown 4 164 (30) 11.8 (0.7) 24.5 (5) 12 (1.1) 93 (53) 8 Algae Dusky brown 5 600 (41) 35.5 (0.5) 25 (2) 27.2 (0.4) 86 (19) 9 Algae Dusky brown 4 453 (67) 33 (2) 22 (2.3) 26.5 (1.4) 55 (19) 10 Algae Dusky brown 3 435 (77) 33 (5) 23 (3) 30.3 (4.8) 35 (6) 11 Algae Dusky brown 1 567 26 18 23.9 42 12 Algae Dusky brown 6 566 (34) 32.3 (1.4) 17.8 (1.5) 29.9 (1.6) 29 (5) 13 Algae Dusky brown 4 600 (29) 33.7 (1.8) 17.7 (1.3) 32.3 (2) 28 (1) 14 Algae Dusky brown 4 727 (42) 32.2 (1) 12.7 (0.7) 31.5 (1) 17 (1) 15 Algae Dusky brown 3 826 (87) 26.2 (0.6) 7.6 (0.6) 25.6 (0.7) 10 (0.4) 16 mild Light green 5 92 (13) 11.3 (0.6) 34.2 (4.4) 15.5 (0.5) 171 (32) 17 mild Light green 5 139 (10) 10.4 (0.5) 23.8 (3) 12.3 (0.5) 110 (0.5) 18 mild green 5 198 (23) 9.8 (0.4) 14.5 (2.1) 9.7 (0.4) 56 (13) 19 mild Dark green 3 254 (63) 9.8 (1.7) 10.3 (7) 10.6 (0.3) 30 (26) 22 mild semi- 3 418 (16) 38.1 (1.3) 25.3 (1.7) 28.8 (1.4) 124 (45) transparent 23 mild Light beige 3 640 (15) 32.1 (1.7) 25 (0.1) 25.1 (0.9) 75 (1) 24 mild beige 4 713 (74) 26.6 (1.8) 23 (2) 24.3 (2.2) 67 (28) 25 mild Dark beige 3 941 (26) 21.4 (1) 17 (0.1) 21.5 (1) 24 (0.8) 28 mild Light green 3 402 (4) 30 (1.5) 32 (2) 31.5 (1.4) 232 (0.9) 29 mild Light green 4 634 (46) 24.3 (1.3) 17 (3) 25.1 (1.3) 36 (6) 30 mild green 5 903 (106) 21.8 (1.4) 6 (1.3) 21.6 (1.4) 6 (1.3) 31 mild Dark green 3 1215 (92) 17.1 (0.5) 3.4 (04) 17.1 (0.5) 3.4 (0.4) 34 none Very light 4 89 (6) 10.6 (0.2) 71 (14) 16.2 (0.6) 355 (34) beige 35 none Light beige 3 134 (5) 9.6 (04) 34 (6) 11.4 (0.3) 169 (64) 36 none beige 3 174 (5) 8.6 (0.2) 22.5 (2.4) 9.6 (0.1) 143 (45) 37 none beige 4 350 (78) 10.4 (05) 9.3 (2.3) 9.4 (0.9) 28 (8) 40 none semi- 5 512 (92) 35.1 (3) 27 (1) 30.8 (1.2) 389 (15) transparent 41 none Light beige 3 582 (84) 28.3 (2.6) 24 (2) 24.4 (1) 66 (22) 42 none Light beige 3 765 (94) 23.8 (1) 24 (4) 21.9 (1) 69 (20) 46 none Light beige 4 403 (38) 26.6 (7) 32 (3) 30.3 (0.8) 160 (22) 47 none Light beige 4 555 (59) 21.8 (1) 19 (3) 22.8 (1.1) 66 (16) 48 none Light beige 4 836 (96) 20.7 (0.9) 7.5 (1.4) 20.5 (1.1) 15 (3) 49 none Light beige 3 1308 (37) 19.2 (07) 3.5 (0.2) 19.2 (0.6) 3.5 (0.2)

(108) The extruded products obtained with the bioplastic compositions 34-37, 40-43, 46-49, containing algal powders according to the invention (example 3) do not give off any bothersome, nauseating or unpleasant odour.

(109) The bioplastic compositions 16-19, 22-25, 28-32, containing algal powders according to example 2, which were prepared according to a process identical to that of example 3 but without the step of reducing the protein content, have a mild odour.

(110) The extruded products obtained with the bioplastic compositions developed from the native starch powder (compositions 1-3) and those developed from algae simply reduced to powder of example 1 (formulations 4-7, 8-11, 12-15), without any treatment, have, respectively, an odour of bread and a strong algae odour.

(111) The process according to the invention is therefore effective in suppressing the odour phenomena.

(112) Regarding colour, the extruded products obtained from algae simply reduced to powder of example 1 (formulations 4-7, 8-11, 12-15) have dusky brown colours. Such colours do not make them usable in the manufacture of the majority of plastic products.

(113) The extruded products obtained with the bioplastic compositions 16-19, 22-25 and 28-31, containing algal powders according to example 2, have light to dark beige colours or light to dark green colours.

(114) Only the compositions 22 and 40 made it possible to obtain a semi-transparent colour. In these formulations, the content of algae is lower than in the compositions 23-25 and 41-43. The polymer is PPC.

(115) In formulation 34, which has the same amount of algae, the colour is a very light beige but less transparent, and the polymer is PBAT. The bioplastic compositions 34-37 and 40-43 will give plastic products for which the colours will not be readily predictable. The addition of a polymer such as PPC is recommended.

(116) The extruded products obtained with the bioplastic compositions 34-37 and 40-43, containing algal powders according to example 3, have light beige colours or are semi-transparent. The formulation 37, containing 55% by weight of algal powder according to the invention, made it possible to obtain a beige extruded product, which is acceptable. Indeed, during the formation of films, the products are stretched and the final colour obtained will depend on the thickness of the film.

(117) Here again, it is noted that the polymer PPC is effective to accentuate transparency.

(118) Among the formulations using PBAT as polymer, it will be noted that the compositions 34-36, developed from algal powders with a reduced protein content, have lower moduli of elasticity than the moduli of the other compositions and much higher breaking strains than with algal powders which have not been deproteinized (16-18). The materials are therefore more flexible with better deformation.

(119) In the formulations using PBS as polymer, it will be noted that the compositions 47-48 with algal powder containing a reduced protein content, have lower moduli of elasticity and much higher breaking strains than with algal powders which have not been deproteinized (28-30); the materials are therefore more flexible with better deformation.

(120) Moreover, the materials with PBS and with the same contents of algae are however more rigid and less deformable than the formulations with PBAT.

(121) In the formulations using PPC, it will be noted that the compositions (40-42), with algal powder containing a reduced protein content, have moduli of elasticity and breaking strains which are equivalent to the algal powders which have not been deproteinized (22-25). The materials incorporating PPC are however more rigid and less deformable than the formulations incorporating PBAT.

EXAMPLE 6: BIOPLASTIC COMPOSITIONS FORMULATED FROM ALGAL POWDERS OBTAINED BY A PROCESS ACCORDING TO THE INVENTION USING ANTI-UV AGENTS, ANTIOXIDANTS, AND ANTI-ODOUR AGENTS

(122) Bioplastic compositions were formulated by mixing the algal powders from examples 2 and 3, PBAT and anti-UV agents, antioxidants and anti-odour agents. In total, four compositions were formulated containing 40% of algal powder.

(123) Table 5 below indicates the compositions of the mixtures produced:

(124) TABLE-US-00006 TABLE 5 Algae Algae Polymer Ex. 2 Ex. 3 Diglycerol PBAT PPC PBS irgafos 168 irganox 1076 96522 PBAT 62 40% 10% 50% 0.20% 0.20% 63 40% 10% 50% 0.20% 0.20% 0.40% PBAT 64 40% 10% 50% 0.20% 0.20% 65 40% 10% 50% 0.20% 0.20% 0.40%

(125) The extrusion conditions were 120, 140, 170 C.-50 rpm

(126) And the injection conditions were 170 C.-8 bar.

(127) Compositions 64 and 65 are less coloured and odourless compared to formulation 62. Formulation 63 is more coloured but the odour is improved compared to formulation 62.

(128) The addition of antioxidant and anti-UV agent improves the colour compared to the compositions of example 4.

(129) The mechanical properties obtained are as follows (Table 6)

(130) TABLE-US-00007 TABLE 6 Compo- Modulus, Threshold Threshold Breaking Breaking sition MPa stress strain strength MPa strain % 62 150 (6) 10.1 (0.7) 21.7 (0.5) .sup.11 (0.8) 70 (26) 63 196 (5) 10.9 (1.5) .sup.15 (5.5) 11.7 (0.7) 40 (7) 64 204 (15) 11.3 (0.9) .sup.18 (0.6) 11.2 (1.1) 40 (6) 65 232 (22) 12 (05) 17.2 (0.4) 11.3 (0.5) 39 (3)

EXAMPLE 7: BIOPLASTIC COMPOSITIONS FORMULATED FROM ALGAL POWDERS OBTAINED BY A PROCESS ACCORDING TO THE INVENTION USING ANOTHER CHELATING AGENT IN THE STEP FOR DESTRUCTURING THE CELL WALLS

(131) The steps of the process according to example 3 were carried out with, in step 4, the following chelating agents: sodium oxalate, sodium carbonate and sodium chloride. The algal powders were mixed with plasticizers and polymers. The molar mass of each mixture was measured. The results are as follows:
a) with sodium oxalate: 570 000 g/mol,
b) with sodium carbonate: 600 000 g/mol,
c) with sodium chloride: 474 000 g/mol,
d) with citric acid: 295 000 g/mol.
The molar mass is halved with citric acid.
Thermal stability tests were also carried out. The 4 products were kept for 3 days at 150 C.: with sodium oxalate, sodium chloride and sodium carbonate: the materials are burnt, with strong caramel odours, with citric acid: the colour remains light yellow.

(132) Citric acid is therefore preferred, because it limits the problems of compatibility with the other compounds. Indeed, the molecular weight was identified, within the context of the present invention, as being a dominant factor for obtaining a good mixture of the polymers, algae, and other compounds. Moreover, it is advisable to give preference to an activating agent which may also be a thermal stabilizer, such as citric acid.