Polyhydroxyalkanoates (PHAs) are biopolymers synthesized and accumulated intracellularly by microorganisms as a reserve of carbon and energy. One of the most developed directions of research in this area is reducing the cost of producing PHA through the use of available carbon raw materials, which can be various compounds. The use of wastes as a substrate for the synthesis of bioplastics can also make a significant contribution to solving this problem. Three sources of waste fish oils (WFOs) were investigated as a C-substrate for the growth of Cupriavidus necator B-10646 bacteria and PHA accumulation: WFO from smoked Baltic sprat heads, WFO from fresh substandard Baltic sprat, and WFO from heads and backbones of fresh Atlantic mackerel. All three studied WFO sources were suitable for the cultivation of C. necator B-10646 bacteria and the synthesis of PHA. The highest bacterial biomass yields were obtained using WFO from smoked sprat heads (4.6 g/L), slightly lower biomass yields were obtained using WFO from fresh mackerel heads and backbones (4.1 g/L). The smallest biomass yield was obtained from the WFO from of fresh sprat (2.2 g/L). The polymer content was close and amounted to 67.0–72.0% by the end of cultivation (72 h) for all variants, and when using WFO from smoked sprat heads, bacteria synthesized copolymer P(3HB-co-3HV-co-3HHx) with a content of monomers 3HV 1.6 mol.% and 3HHx 0.3 mol.%. When two other types of WFO were used, the P(3HB) homopolymer was obtained. WFO obtained from three different sources (fat from smoked sprat heads, fresh sprat and heads and backbones mackerel) are promising substrates for the synthesis of polyhydroxyalkanoates of various compositions by the bacteria C. necator B-10646.

Conflicts of interest:
The authors declare that they have no conflict of interest in the publication of this article. The authors have no conflicts of interest to report in this work. Abstract was not submitted elsewhere and was first published here.

Funding:
The study was funded by the Russian Science Foundation (grant number 23-64-10007).