Fecha de publicación: -- Fuente: PubMed "industrial biotechnology" Bioresour Technol. 2026 Nov 9:136212. doi: 10.1016/j.biortech.2026.136212. Online ahead of print.ABSTRACTPolyhydroxyalkanoates (PHAs) are widely recognized as promising alternatives to conventional petroleum-based plastics due to their superior biocompatibility and complete biodegradability. Here, we report that Halomonas nigrificans X339 is capable of producing polyhydroxybutyrate (PHB) from lactate-rich wastewater, including low-quality lactate and yellow water. This strain exhibited remarkable tolerance to both D- and l-lactate, up to 60 g/L and 40 g/L, respectively. In shake flask fermentations, X339 produced 5.16 g/L and 5.12 g/L PHB from 20 g/L d-lactate and l-lactate, respectively. Furthermore, in open, and non-sterile fermentations using low-quality lactate and yellow water, X339 achieved PHB titers of 2.66 g/L and 1.70 g/L, respectively. Optimization of the nitrogen source concentration further enhanced the titers to 3.03 g/L and 2.43 g/L. Subsequently, we further engineered the exopolysaccharide-deletion strain X339ΔPS1 by knocking out the PHA granule-associated protein gene (phaP) or/and PHA depolymerase gene (phaZ). The resulting strain, X339ΔPS1ΔphaZ, emerged as the superior PHB producer, yielding 6.90 g/L and 6.71 g/L PHB from 20 g/L d-lactate and l-lactate, respectively. When cultivated on low-quality lactate and yellow water, this strain achieved enhanced PHB titers of 4.38 g/L and 4.16 g/L. To the best of our knowledge, this represents the highest titer achieved from lactate or lactate-rich waste streams at the shake-flask level. Collectively, these findings validate the feasibility of converting lactate-rich waste streams into PHB using engineered H. nigrificans chassis at shake-flask scale, laying the foundation for subsequent scale-up to controlled bioreactor cultivation.PMID:43003317 | DOI:10.1016/j.biortech.2026.136212