Production of single-cell-protein (SCP) / poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) matrices through fermentation of archaea <i>Haloferax mediterranei</i>

Abstract The idea of in-situ integrating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) sieves in a single-cell protein (SCP) represents a promising approach to enhance the properties of microbial biomass as protein alternatives. Archaea SCP/PHBV matrix was successfully produced with a concentration of 8.0 ± 0.1 g L -1 and a productivity of 11.1 mg L -1 h -1 using Haloferax mediterranei . This was achieved by employing 30 g L -1 of enzymatically hydrolyzed bread waste (BW) and 200 g L -1 of red sea salt at 42 °C and with shaking at 150 rpm for 3 days. The amino acid profile of the SCP/PHBV matrix revealed a total amino acid content of 358 g kg -1 , including 147 g kg -1 of essential amino acids. The protein quality of the H. mediterranei SCP/PHBV matrix was assessed using the in-vitro enzyme digestion method, indicating a high-quality protein with an in-vitro digestibility value of 0.91 and a protein digestibility-corrected amino acid score (PDCAAS) of 0.78. The PHBV component (36.0 ± 6.3% w/w) in the SCP/PHBV matrix consisted of a copolymer of 3-hydroxybutyrate and 3- hydroxyvalerate in a 91:9 mol% ratio, respectively. The simultaneous production of PHBV polymeric sieves within the H. mediterranei SCP/PHBV matrix provides an alternative protein source with enhanced physicochemical and thermal properties. Highlights SCP/PHBV matrices were produced from wasted bread by archaea H. mediterranei . This is the first report that explored the production and properties of SCP/PHBV. The presence of PHBV in SCP affected its physicochemical and thermal properties. SCP/PHBV with high-quality protein was achieved with a PDCAAS value of 0.78. Graphical abstract