The present invention provides a genetically modified lactic acid bacterium capable of producing diacetyl under aerobic conditions. Additionally the invention provides a method for producing diacetyl using the genetically modified lactic acid bacterium under aerobic conditions in the presence of a source of iron-containing porphyrin and a metal ion selected from Fe.sup.3+, Fe.sup.2+ and Cu.sup.2+. The lactic acid bacterium is genetically modified by deletion of those genes in its genome that encode polypeptides having lactate dehydrogenase (E.C 1.1.1.27/E.C.1.1.1.28); -acetolactate decarboxylase (E.C 4.1.1.5); water-forming NADH oxidase (E.C. 1.6.3.4); phosphotransacetylase (E.C.2.3.1.8) activity; and optionally devoid of or deleted for genes encoding polypeptides having diacetyl reductase ((R)-acetoin forming; EC:1.1.1.303); D-acetoin reductase; butanediol dehydrogenase ((R,R)-butane-2,3-diol forming; E.C. 1.1.1.4/1.1.1.-) and alcohol dehydrogenase (E.C. 1.2.1.10) activity. The invention provides for use of the genetically modified lactic acid bacterium for the production of diacetyl and a food product.

The present invention relates to a process of producing isobutanol, including: mixing water, lactate, an enzyme mixture including at least one enzyme, at least one cofactor, and at least one coenzyme, to prepare a reaction mixture; allowing catalytic conversions of lactate in the reaction mixture for a sufficient amount of time to produce isobutanol; and separating the isobutanol from a reactant obtained by the catalytic conversions, in which the conversion of lactate into isobutanol is in association with a NADH.sup.+/NADH and/or NADP.sup.+/NADPH regenerating system.

The present invention relates to a process for producing an organic acid by fermentation, comprising the process steps: I) cultivating microorganisms in a culture medium to which are fed, as assimilable carbon sources, glycerol and a further carbonaceous compound, to allow the microorganisms to produce the organic acid, thereby obtaining a fermentation broth comprising the organic acid; II) recovering the organic acid or the salt thereof from the fermentation broth obtained in process step I); wherein, at least for a certain period of time in process step I), the consumption rate of the further carbonaceous compound (C.sub.Rc.c.; in g per liter per hour) is lower than the maximum theoretical consumption rate of the further carbonaceous compound (CR.sub.c.c. max; in g per liter per hour).

A method for producing lactic acid from a biomass-based material includes: cultivating a strain of Bacillus spp. or recombinant Candida spp. capable of yielding lactic acid by consumption of hexose and pentose in a seed medium containing molasses and corn steep liquor, so as to obtain a seed culture of the strain in the seed medium; and fermenting the biomass-based material with the seed culture of the strain. The biomass contains a fermentable sugar. Genomic DNA of the recombinant Candida spp. includes a gene encoding lactate dehydrogenase, and pdc gene in the genomic DNA of the recombinant Candida spp. is deleted, disrupted or disabled.

Provided herein are gene editing systems and/or compositions comprising RNA guides targeting LDHA for use in genetic editing of the LDHA gene. Also provide herein are methods of using the gene editing system for introducing edits to the LDHA gene and/or for treatment of primary hyperoxaluria (PH), and processes for characterizing the gene editing system.

A system and method for controlling metabolic enzymes or pathways in cells to produce a chemical above the levels of a wild-type strain is disclosed. The system utilizes cells, including yeasts, bacteria, and molds, having at least two genes capable of being controlled bi-directionally with light, where one gene is turned from off to on when exposed to light and another gene is turned from on to off when exposed to light, the two genes reversing when the light is turned off. Cells may utilize any number of sequences that benefit chemical production, including sequences that: encode for constitutive transcription of light-activated transcription factor fusions; encode for a metabolic enzyme; encode for a repressor; induce expression of metabolic enzymes; and an endogenous or exogenous activator expressed by a constitutive promoter, inducible promoter, or gene circuit. These systems may be coupled to biosensors or protein cascade systems, enabling the monitoring or automation of the fermentation process to optimize production of a desired product. These systems may also allow for optimization and periodic operation of a bioreactor using light pulses.

Disclosed are a recombinant acid-resistant yeast having improved lactic-acid-producing ability and a method of preparing lactic acid using the same. When producing lactic acid using the recombinant acid-resistant yeast according to the present invention, not only lactic-acid fermentation can be performed with lactic-acid-producing ability similar to that of bacterial fermentation using a remarkably smaller amount of a neutralizing agent than in the case of conventional bacterial fermentation, but also the production of ethanol and glycerol which are byproducts can be reduced. Thus, fermentation costs can be greatly reduced and the cost of subsequent purification processes can be reduced.

The present disclosure discloses an engineering strain and application thereof in joint production of Danshensu and alanine, and belongs to the technical field of bioengineering. The present disclosure constructs a three-enzyme co-expression genetic engineering strain, and realizes joint production of Danshensu and alanine. Further, the transport of a substrate is promoted and decomposition of products is reduced by knocking out or enhancing expression of related genes on E. coli genome. The genetic engineering strain provided by the present disclosure can produce optically pure D-danshensu and L-danshensu, and jointly produce pyruvic acid. The production process is simple, raw materials are easily available, impurities are fewer, and a good industrial application prospect is achieved.

The present disclosure discloses a production method of Danshensu, belonging to the technical field of bioengineering. The present disclosure constructs a novel genetic engineering strain co-expressed by three enzymes, which can be applied to the production of optically pure 3-(3,4-dihydroxyphenyl)-2-hydroxypropionic acid. All of the (D/L)--hydroxycarboxylic acid dehydrogenase selected by the present disclosure have the characteristics of poor substrate specificity and strong optical specificity, and can produce optically pure D-danshensu and L-danshensu. Further, the production efficiency of the recombinant strain is improved by knocking out or enhancing the expression of a related gene on the E. coli genome to promote substrate transport and reduce product decomposition. The method for producing Danshensu and -ketoglutaric acid by using the transformation of the recombinant strain according to the present disclosure is simple, has easily available raw materials, few impurities, and has good industrial application prospects.

Disclosed are very high optically pure D- and L-lactic acid fermentation production strains and construction methods thereof and the method for preparing very high optically pure D- and L-lactic acids using the strains, wherein the deposit number of the D-lactic acid fermentation production strain is CGMCC No. 11059, and the deposit number of the L-lactic acid fermentation production strain is CGMCC No. 11060.