Optimization of polyhydroxyalkanoate biopolymer production from lignocellulosic wood waste using statistical experimental designs.

Plastic pollution, resulting from the persistence of conventional polymers, remains a critical environmental challenge that necessitates the development of biodegradable alternatives. Polyhydroxyalkanoates (PHAs) represent an attractive solution, being naturally synthesized by microorganisms under nutrient-limited conditions. This study investigates the production of PHAs using lignocellulosic wood waste, specifically sal and teak residues, as an economical carbon source. Fermentable sugars were obtained via dilute sulfuric acid hydrolysis (10% w/v biomass with 4% v/v HSO), incubated at 120 °C for 1 h, and filtered to yield a hydrolysate containing approximately ~ 36 mg/mL total reducing sugars (DNS assay). The hydrolysate served as the carbon source in bioprocess optimization (optimal carbon concentration: 2.50%, equivalent to 25 g/L). Potential PHA-producing isolates were screened using Nile Blue and Sudan Black staining. The most efficient producer, Klebsiella pneumoniae strain DSM 30,104 (MK2023), confirmed through 16 S rRNA sequencing, demonstrated notable PHA accumulation. Process parameters-including carbon and nitrogen concentrations and Temperature-were optimized through Plackett-Burman Design (PBD) followed by Response Surface Methodology (RSM) using a face-centered central composite design. Optimal production was achieved at 2.50% carbon, 0.105% nitrogen, and 34 °C, yielding 5.7 mg/mL PHA after 72 h with 10% (v/v) inoculum. UV-Vis and FTIR analyses confirmed the polymer's identity as polyhydroxybutyrate (PHB). The study highlights wood waste as a viable, low-cost substrate for PHA synthesis, promoting sustainable biopolymer production while advancing circular bioeconomy practices.