Co-utilization of amino acid-rich wastes and glycerol for microbial lipid production

Microbial lipids are considered to be potential raw materials for biodiesel production. However, the costs of such a process remain high due to the use of expensive feedstocks for microbial lipid production. The meat industry and biodiesel refineries generate amino acid (AA) wastes and crude glycerol, respectively, which could be explored as relatively cheap feedstocks for oleaginous yeasts. Unfortunately, AA wastes have a high nitrogen content and crude glycerol contains several impurities, discouraging microbial lipid production. Here, glycerol was co-used with AA, or with AA blends with compositional profiles matching those of different meats, so that the media had favorable carbon-to-nitrogen (C/N) ratios to promote AA conversion into lipids using the oleaginous yeast Cryptococcus curvatus ATCC 20509 under two-stage culture conditions. Co-utilization of glycerol and AA resulted in improved lipid production. The highest lipid yield of 20.9 g 100 g(-1) was achieved with lysine and glycerol, where the lipid yield was 13.9 g 100 g(-1), using an AA blend of similar composition to sheep viscera and glycerol. The lipid products comprised over 93% of 16 and 18 carbon-containing fatty acids, showing high potential for biodiesel production. The co-use of glycerol with AA improved AA conversion into lipids while decreasing the inhibitory effects at relatively high AA concentrations. The utilization of crude glycerol and AA-rich wastes from the meat industry could help both the development of biorefineries and waste minimization. (c) 2021 Society of Chemical Industry and John Wiley & Sons, Ltd