Waste Fish Oil is a Promising Substrate for Productive Synthesis of Degradable Polyhydroxyalkanoates

Abstract

Waste fish oils (WFOs) obtained from the wastes of Sprattus balticus and Scomber scombrus have been investigated as a new substrate for the synthesis of polyhydroxyalkanoates (PHA). WFOs produced by thermal or enzymatic methods had some differences in the ratio of fatty acids and lipid saturation. C. necator B-10,646 bacteria, grown in a laboratory Bio-Flo fermenter with high mass transfer characteristics and a high degree of emulsification of WFO fat, provided high productivity in all variants, superior to other substrates (sugars, glycerol, etc.). The total yield of bacterial biomass and PHA content obtained on WFO from smoked sprat heads by thermal or enzymatic method was 87.4 and 109.7 g/L and 75.6 and 81.0%, respectively, for 30 h of cultivation, which slightly exceeded the results obtained using WFO from fresh mackerel heads. Under studied conditions, bacteria utilized the entire spectrum of fatty acids in WFO lipids including polyenoic and saturated fatty acids. This ensured a high degree of utilization of WFOs by bacteria (92.3–94.7%). The synthesized PHA samples were represented by poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) with similar degrees of crystallinity, molecular weight and temperature characteristics. The studied WFOs can be recommended as a new and renewable substrate for productive synthesis of PHA.