Valorization of glycerol from biodiesel industries as a renewable substrate for co-producing probiotic bacteria biomass and acetic acid

Abstract

Glycerol, a byproduct from oil-based biodiesel industries, has been used as carbon and energy sources for growing Lactobacillus strains with probiotic characteristics. For such a purpose, crude glycerol (70.6 %) was subjected to a pretreatment with different inorganic acids to remove soap, free fatty acids, and other impurities. The best performance was attained with phosphoric acid at pH 4.0, thus resulting in treated samples containing glycerol whose levels were higher than 96 wt%. The treated glycerol was used to formulate the culture medium and assess the ability of 15 Lactobacillus strains to assimilate it. High cell yields (0.34, 0.28, and 0.25 g cell g−1 glycerol) were achieved by Lactobacillus delbrueckii UFV-H2b20, Lactobacillus acidophilus ATCC 4356, and Lactobacillus plantarum ATCC 8014 strains, respectively. Kinetic profiles in medium containing potassium phosphate buffer solution (pH 6.0) showed similar growth (yields ranging from 0.29–0.31 g g−1) and acetic acid production (yields ranging from 0.33–0.34 g g−1) for the selected lactobacilli bacteria. These results reveal that biodiesel-derived glycerol represents a potential substrate for growing probiotic strains, thence obtaining value-added products.