Microbial lipid and biodiesel production from municipal sludge fortified with crude glycerol medium using pH-based fed-batch strategy

To achieve a good performance in fed-batch fermentation, the feeding strategy is essential and important. In this study, pH-based (pH 6.0) fed-batch fermentation has been conducted on municipal sludge fortified with crude glycerol medium using Y. lipolytica SKY7 (YL). No additional nitrogen source and trace elements had to be added as secondary municipal sludge had sufficient nitrogen and trace elements to support growth of YL. At 72 h of fedbatch fermentation, high biomass (59.67 g/L) and lipid concentration (31.44 g/L) was obtained. The biodiesel produced using sludge cultivated YL had similar fatty acid ester profile as that of vegetable oil. It was revealed from energy balance that biodiesel production using pH-based fed-batch strategy was energetically favorable and has unit production cost of 0.67 $/L B10.

Automated summary

This study conducted fed-batch fermentation at pH 6.0 using municipal sludge and crude glycerol to cultivate Y. lipolytica SKY7, resulting in high biomass and lipid concentration. The biodiesel produced from sludge-cultivated YL had a similar fatty acid ester profile as vegetable oil.