Microbial community engineering for biopolymer production from glycerol.

In this work, the potential of using microbial community engineering for production of polyhydroxyalkanoates (PHA) from glycerol was explored. Crude glycerol is a by-product of the biofuel (biodiesel and bioethanol) industry and potentially a good substrate for bioplastic production. A PHA-producing microbial community was enriched based on cultivation in a feast-famine regime as successfully applied before for fatty acids-based biopolymer production. A glycerol-fed sequencing batch reactor operated at a 2-day liquid and biomass residence time and with feast-famine cycles of 24 h was used to enrich a mixed community of PHA producers. In a subsequent fed-batch PHA production step under growth-limiting conditions, the enriched mixed community produced PHA up to a dry weight content of 80 wt.%. The conversion efficiency of substrate to PHA on electron basis was 53%. Since glycerol is entering the metabolic pathways of the cell in the glycolytic pathway, it was anticipated that besides PHA, polyglucose could be formed as storage polymer as well. Indeed, polyglucose was produced in low amounts (∼ 10 wt.%). The results indicated that the feast-famine-based enrichment strategy was comparably successful to obtain a microbial community compared to fatty acids-based enrichment described before.