One-step biosynthesis of α-ketoisocaproate from l-leucine by an Escherichia coli whole-cell biocatalyst expressing an l-amino acid deaminase from Proteus vulgaris

摘要

This work aimed to develop a whole-cell biotransformation process for the production of α-ketoisocaproate from L -leucine. A recombinant Escherichia coli strain was constructed by expressing an L -amino acid deaminase from Proteus vulgaris . To enhance α-ketoisocaproate production, the reaction conditions were optimized as follows: whole-cell biocatalyst 0.8?g/L, leucine concentration 13.1?g/L, temperature 35?°C, pH 7.5, and reaction time 20?h. Under the above conditions, the α-ketoisocaproate titer reached 12.7?g/L with a leucine conversion rate of 97.8%. In addition, different leucine feeding strategies were examined to increase the α-ketoisocaproate titer. When 13.1?g/L leucine was added at 2-h intervals (from 0 to 22?h, 12 addition times), the α-ketoisocaproate titer reached 69.1?g/L, while the leucine conversion rate decreased to 50.3%. We have developed an effective process for the biotechnological production of α-ketoisocaproate that is more environmentally friendly than the traditional petrochemical synthesis approach.