L-Cysteine Metabolism and Fermentation in Microorganisms.
L-Cysteine Metabolism and Fermentation in Microorganisms.
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DOI：
10.1007/10_2016_29
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发表时间：
2016-11
期刊：
影响因子：
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通讯作者：
H. Takagi;I. Ohtsu
中科院分区：
文献类型：
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作者：
H. Takagi;I. Ohtsu
l-Cysteine is an important amino acid both biologically and commercially. Although most amino acids are industrially produced by microbial fermentation,l-cysteine has been mainly produced by protein hydrolysis. Due to environmental and safety problems, synthetic or biotechnological products have been preferred in the market. Here, we reviewedl-cysteine metabolism, including biosynthesis, degradation, and transport, and biotechnological production (including both enzymatic and fermentation processes) ofl-cysteine. The metabolic regulation ofl-cysteine including novel sulfur metabolic pathways found in microorganisms is also discussed. Recent advancement in biochemical studies, genome sequencing, structural biology, and metabolome analysis has enabled us to use various approaches to achieve direct fermentation ofl-cysteine from glucose. For example, worldwide companies began to supplyl-cysteine and its derivatives produced by bacterial fermentation. These companies successfully optimized the original metabolism of their private strains. Basically, a combination of three factors should be required for improvingl-cysteine fermentation: that is, (1) enhancing biosynthesis: overexpression of the alteredcysEgene encoding feedback inhibition-insensitivel-serineO-acetyltransferase (SAT), (2) weakening degradation: knockout of the genes encodingl-cysteine desulfhydrases, and (3) exploiting export system: overexpression of the gene involved inl-cysteine transport. Moreover, we found that “thiosulfate” is much more effective sulfur source than commonly used “sulfate” forl-cysteine production inEscherichia coli, because thiosulfate is advantageous for saving consumption of NADPH and relating energy molecules.
