A method for preparing glucosamine includes the steps of converting fructose-6-phosphate (F6P) and an ammonium salt to glucosamine-6-phosphate (GlcN6P) under the catalysis of glucosamine-6-phosphate deaminase (EC 3.5.99.6, GlmD); and producing glucosamine (GlcN) by the dephosphorylation of GlcN6P under the catalysis of an enzyme capable of catalyzing the dephosphorylation. Such a method can be used to prepare glucosamine by in vitro enzymatic biosystem.

Recombinant strains are obtained for the production of allulose, allose, and allitol by regulating intracellular glucose metabolism, reducing the enzyme activity of fructose 6-phosphate kinase, and enhancing the enzyme activities of glucokinase and glucose-6-phosphate isomerase, allulose 6-phosphate 3-epimerase, allulose 6-phosphate phosphatase, fructose permease and fructokinase, and optionally enhancing the enzyme activities of ribose 5-phosphate isomerase, allose 6-phosphate phosphatase, ribitol dehydrogenase, glycerol permease, glycerol dehydrogenase, and dihydroxyacetone kinase. A method for producing allulose and allose is an extracellular multienzyme cascade method. Multienzyme cascade catalysis and fermentation are coupled to improve the conversion rate of starch sugar or sucrose to the synthesized allulose.

The current disclosure provides a process for enzymatically converting a saccharide into allulose. The invention also relates to a process for preparing allulose where the process involves converting fructose 6-phosphate (F6P) to allulose 6-phosphate (A6P), catalyzed by allulose 6-phosphate 3-epimerase (A6PE), and converting the A6P to allulose, catalyzed by allulose 6-phosphate phosphatase (A6PP).

Disclosed is a new tagatose 6-phosphate 4-epimerase, which is capable of converting fructose 6-phosphate into tagatose 6-phosphate and vice versa. Also disclosed is an application of the enzyme in tagatose production.

The current disclosure provides a process for enzymatically converting a saccharide into allulose. The invention also relates to a process for preparing allulose where the process involves converting fructose 6-phosphate (F6P) to allulose 6-phosphate (A6P), catalyzed by allulose 6-phosphate 3-epimerase (A6PE), and converting the A6P to allulose, catalyzed by allulose 6-phosphate phosphatase (A6PP).

Provided herein, in some embodiments, are systems, methods, and compositions (e.g., cells and cell lysates) for enzymatically converting a polymeric glucose carbohydrate (e.g., starch) to sugar.

The current disclosure provides a process for enzymatically converting a saccharide into allulose. The invention also relates to a process for preparing allulose where the process involves converting fructose 6-phosphate (F6P) to allulose 6-phosphate (A6P), catalyzed by allulose 6-phosphate 3-epimerase (A6PE), and converting the A6P to allulose, catalyzed by allulose 6-phosphate phosphatase (A6PP).

The present disclosure provides a Bacillus subtilis strain, a recombinant B. subtilis strain and use thereof, belongs to the technical field of microbial fermentation. B. subtilis strain RF1-6 provided by the present disclosure is a mutant strain with the highest riboflavin yield screened by gene modification and mutagenesis using a high riboflavin-producing strain RF1 as a starting strain, deposited at China Center for Type Culture Collection (CCTCC) under accession number M 2022565. Riboflavin yield can be increased by 22.8% compared with that of the high riboflavin-producing strain RF1.

A method for preparing a yeast capable of simultaneously fermenting a pentose and a hexose sugar, comprising: (a) providing a yeast comprising: one or more heterologous genes encoding an enzyme of a pentose metabolic pathway; disruptions of a gene encoding a ribulose-phosphate 3-epimerase and of a gene encoding a glucose-6-phosphate isomerase; one or more overexpressed endogenous genes encoding an enzyme of the pentose phosphate pathway; and a disruption of one or more genes encoding an NADPH dependent 6-phosphogluconate dehydrogenase, (b) subjecting said yeast to evolutionary engineering on a medium comprising a hexose sugar and at least one pentose sugar, selecting for a yeast with improved growth rate obtain an evolved yeast; (d) restoring, in the evolved yeast, one or more of the disrupted genes, or: (d) identifying genetic permutations in at least part of the genome of the evolved yeast by genome sequencing; (e) constructing an improved pentose and hexose-fermenting yeast comprising one or more said genetic permutations. Also described is a recombinant yeast comprising one or more heterologous genes of a pentose metabolic pathway, and a gene encoding a variant of a parent polypeptide, the variant comprising an amino acid sequence comprising at least one mutation, when aligned with the amino acid sequence in SEQ ID NO: 6.

Disclosed herein are methods of producing hexoses from saccharides by enzymatic processes. The methods utilize fructose 6-phosphate and at least one enzymatic step to convert it to a hexose.