Biosynthesis and characterization of PHB-b-PHV by Marinobacterium sediminicola through dual regulation of substrate...

While polyhydroxyalkanoate block copolymers offer a sustainable route to advanced biodegradable materials, precise architectural control remains challenging. Here, we report Marinobacterium sediminicola CGMCC 1.7287 as a distinctive host for PHB-b-PHV biosynthesis via the dual regulation of volatile fatty acid (VFA) concentration and feeding sequence. M. sediminicola exhibits highly pronounced VFA-assimilation behavior, exclusively producing PHB from butyrate while directly converting valerate into PHV-rich polymers. By regulating VFA concentration to minimize substrate crossover and dictating the feeding sequence, distinct polymer architectures were selectively obtained, including random copolymers (statistically distributed monomers), physical blends (unlinked homopolymers), and block copolymers (covalently linked PHB and PHV segments). Notably, sequential valerate-to-butyrate feeding produced an NMR-assigned PHB-b-PHV at 3.49 g/L within 48 h, demonstrating highly favorable temporal efficiency at the flask scale. The PHB-b-PHV copolymer exhibited limited molecular-weight heterogeneity and displayed architecture-dependent thermal and mechanical properties distinct from those of the random copolymer and blend. Ultimately, this work uncovers the distinctive VFA-assimilation profile of M. sediminicola and provides a proof-of-concept fermentation strategy for modulating PHB/PHV composition and NMR-assigned architecture under controlled VFA-feeding conditions.