Production of microbial biomass protein from mixed substrates by sequential culture fermentation of Candida utilis and Brevibacterium lactofermentum

Abstract

The aim of the current study was to apply a mixed culture of Candida utilis and Brevibacterium lactofermentum instead of using a mono-culture of B. lactofermentum or yeast to produce higher amount of amino acids, crude protein and true protein by using the maximum amount of substrate mixture, which B. lactofermentum alone cannot utilize. This mixed culture offered a combination that yielded high crude protein content and converted the substrate mixture efficiently into microbial biomass protein. Best results were obtained with sequential fermentation carried out with B. lactofermentum added after 3 days to C. utilis culture grown on beet pulp hydrolysate supplemented with molasses and glucose. Mixed culture of C. utilis and B. lactofermentum maintained the properties of each individual fermentation, with high production of microbial biomass protein in optimized medium. Crude protein increased from 11.3% to 54.5% and dry cell mass to 48 g/L with mixed culture. The amino acid profile of the final microbial biomass protein obtained by mixed culture of C. utilis and B. lactofermentum in a 75-L fermentor remained unchanged, and was enriched with all essential and non-essential amino acids. Mixed culture in this study thus exhibits a synergistic effect with possible industrial application. © Springer-Verlag and the University of Milan 2011.