Synthesis of Sugars by Hydrolysis of Hemicelluloses- A Review

Mannitol, a naturally occurring polyol (sugar alcohol), is widely used in the food, pharmaceutical, medical, and chemical industries. The production of mannitol by fermentation has become attractive because of the problems associated with its production chemically. A number of homo- and heterofermentative lactic acid bacteria (LAB), yeasts, and filamentous fungi are known to produce mannitol. In particular, several heterofermentative LAB are excellent producers of mannitol from fructose. These bacteria convert fructose to mannitol with 100% yields from a mixture of glucose and fructose (1:2). Glucose is converted to lactic acid and acetic acid, and fructose is converted to mannitol. The enzyme responsible for conversion of fructose to mannitol is NADPH- or NADH-dependent mannitol dehydrogenase (MDH). Fructose can also be converted to mannitol by using MDH in the presence of the cofactor NADPH or NADH. A two enzyme system can be used for cofactor regeneration with simultaneous conversion of two substrates into two products. Mannitol at 180 g l−1 can be crystallized out from the fermentation broth by cooling crystallization. This paper reviews progress to date in the production of mannitol by fermentation and using enzyme technology, downstream processing, and applications of mannitol.

https://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=48481&content=PDF

Biotechnological production of mannitol and its applications

A revolution in industrial microbiology was sparked by the discoveries of ther double-stranded structure of DNA and the development of recombinant DNA technology. Traditional industrial microbiology was merged with molecular biology to yield improved recombinant processes for the industrial production of primary and secondary metabolites, protein biopharmaceuticals and industrial enzymes. Novel genetic techniques such as metabolic engineering, combinatorial biosynthesis and molecular breeding techniques and their modifications are contributing greatly to the development of improved industrial processes. In addition, functional genomics, proteomics and metabolomics are being exploited for the discovery of novel valuable small molecules for medicine as well as enzymes for catalysis. The sequencing of industrial microbal genomes is being carried out which bodes well for future process improvement and discovery of new industrial products.

/pdf/recombinant-organisms-for-production-of-industrial-products-95f5alqjkr.pdf

Recombinant organisms for production of industrial products

Confronted with the gradual and inescapable exhaustion of the earth's fossil energy resources, the bio-based process to produce platform chemicals from renewable carbohydrates is attracting growing interest. Escherichia coli has been chosen as a workhouse for the production of many valuable chemicals due to its clear genetic background, convenient to be genetically modified and good growth properties with low nutrient requirements. Rational strain development of E. coli achieved by metabolic engineering strategies has provided new processes for efficiently biotechnological production of various high-value chemical building blocks. Compared to previous reviews, this review focuses on recent advances in metabolic engineering of the industrial model bacteria E. coli that lead to efficient recombinant biocatalysts for the production of high-value organic acids like succinic acid, lactic acid, 3-hydroxypropanoic acid and glucaric acid as well as alcohols like 1,3-propanediol, xylitol, mannitol, and glycerol with the discussion of the future research in this area. Besides, this review also discusses several platform chemicals, including fumaric acid, aspartic acid, glutamic acid, sorbitol, itaconic acid, and 2,5-furan dicarboxylic acid, which have not been produced by E. coli until now.

Metabolic engineering of Escherichia coli for biotechnological production of high-value organic acids and alcohols

Mannitol is a fructose-derived, 6-carbon sugar alcohol that is widely found in bacteria, yeasts, fungi, and plants. Because of its desirable properties, mannitol has many applications in pharmaceutical products, in the food industry, and in medicine. The current mannitol chemical manufacturing process yields crystalline mannitol in yields below 20 mol% from 50% glucose/50% fructose syrups. Thus, microbial and enzymatic mannitol manufacturing methods have been actively investigated, in particular in the last 10 years. This review summarizes the most recent advances in biological mannitol production, including the development of bacterial-, yeast-, and enzyme-based transformations.

Recent advances in the biological production of mannitol

Recently, we reported on the construction of a whole-cell biotransformation system in Escherichia coli for the production of D: -mannitol from D: -fructose. Supplementation of this strain with extracellular glucose isomerase resulted in the formation of 800 mM D: -mannitol from 1,000 mM D: -glucose. Co-expression of the xylA gene of E. coli in the biotransformation strain resulted in a D: -mannitol concentration of 420 mM from 1,000 mM D: -glucose. This is the first example of conversion of D: -glucose to D: -mannitol with direct coupling of a glucose isomerase to the biotransformation system.

Björn Kaup

Papers

D-Mannitol formation from D-glucose in a whole-cell biotransformation with recombinant Escherichia coli

Oxyfunctionalization of α-pinene in a whole-cell bioprocess using recombinant P450 BM-3