Optimization of L-alanine production in the recombinant Pediococcus acidilactici BD16 (alaD+)

Abstract

L-alanine has an extensive array of applications in the food and pharmaceutical industries. However, its commercial utilization is still limited due to reasons like high production costs, poor substrate availability, slower fermentations, lower productivity and lesser purity. In the present study, a Generally Recognized As Safe (GRAS) Pedicoccus acidilactici BD16 (alaD+) strain was employed for the microbial synthesis of L-alanine. Primarily, a considerable enhancement of L-alanine production in the recombinant P. acidilactici BD16 (alaD+) was achieved through a batch fermentation process optimized using one variable approach and Response Surface Methodology. To further enhance L-alanine titers in the recombinant P. acidilactici BD16 (alaD+), a single phase fed-batch fermentation process was also employed and 261.3 g/L (2934 mM) L-alanine production was achieved within 48 h under optimized conditions. After extraction and crystallization, 94% crystal L-alanine (245.8 g/L; 2758 mM) was recovered from the culture broth with an enantiomeric purity of 97.3%. Owing to its high fermentative productivity, the recombinant P. acidilactici BD16 (alaD+) strain based L-alanine production bioprocess offers a great commercial potential and will eventually help in the global expansion of the microbial L-alanine market.