Biosynthesis and characterization of terpolymer P(3HB--3HV--4HB) produced by USMAA1020 using glycerol pitch.

This study demonstrates a circular economy approach by utilizing glycerol pitch, biodiesel co-product as a carbon source to produce biodegradable terpolymer poly(3-hydroxybutyrate--3-hydroxyvalerate--4-hydroxybutyrate) [P(3HB--3HV--4HB)] using USMAA1020. Various carbon sources, including oleic acid, 1,4-butanediol, and 1-pentanol, were combined with glycerol pitch as main substrates. The experiments were conducted in a mineral salt medium (MSM) with a high concentration of carbon source and limited nitrogen, which promotes both bacterial growth and PHA accumulation. Preliminary studies indicated, the composition of the polymer was triggered by varying the concentration of 1,4-butanediol, oleic acid, and glycerol pitch while keeping the amount of 1-pentanol constant. After optimization, the PHA content in dry biomass increased from 60 ± 12 to 88 ± 5 wt%, while the residual dry cell weight (RDCW) slightly decreased from 1.77 ± 0.53 to 1.11 ± 0.41 g/L. The combination of glycerol pitch in the biosynthesis of the terpolymer proved effective for the cost-efficient and sustainable production of P(3HB--3HV--4HB). This process could drive innovation while reducing waste, by harnessing glycerol pitch's properties, sustainable co-product of biodiesel production into a valuable biodegradable polymer. The characterization of the terpolymer revealed a diverse range of properties, making it suitable for various applications.