Abstract：
Microbial production of polyhydroxyalkanoate (PHA) is greatly restricted by high production cost arising from high-temperature sterilization and expensive carbon sources. In this study, a low-cost PHA production platform was established from Halomonas cupida J9. First, a marker-less genome-editing system was developed in H. cupida J9. Subsequently, H. cupida J9 was engineered to efficiently utilize xylose for PHA biosynthesis by introducing a new xylose metabolism module and blocking xylonate production. The engineered strain J9UΔxylD-P8xylA has the highest PHA yield (2.81 g/L) obtained by Halomonas with xylose as the sole carbon source so far. This is the first report on the production of short- and medium-chain-length (SCL-co-MCL) PHA from xylose by Halomonas. Interestingly, J9UΔxylD-P8xylA was capable of efficiently utilizing glucose and xylose as co-carbon sources for PHA production. Furthermore, fed-batch fermentation of J9UΔxylD-P8xylA coupled to a glucose/xylose co-feeding strategy reached up to 12.57 g/L PHA in a 5-L bioreactor under open and unsterile condition. Utilization of corn straw hydrolysate as the carbon source by J9UΔxylD-P8xylA reached 7.0 g/L cell dry weight (CDW) and 2.45 g/L PHA in an open fermentation. In summary, unsterile production in combination with inexpensive feedstock highlights the potential of the engineered strain for the low-cost production of PHA from lignocellulose-rich agriculture waste.
摘要：
微生物生产聚羟基链烷酸酯(PHA)受到高温灭菌产生的高生产成本和昂贵碳源的极大限制。在这项研究中,从HalomonascupidaJ9建立了低成本的PHA生产平台。首先,H.cupidaJ9开发了一种无标记的基因组编辑系统。随后，H.cupidaJ9被设计为通过引入新的木糖代谢模块并阻断木聚糖酸的产生来有效地利用木糖用于PHA生物合成。迄今为止，工程化菌株J9UΔxylD-P8xylA具有由Halomonas以木糖作为唯一碳源获得的最高PHA产量（2.81g/L）。这是关于Halomonas从木糖生产短链和中链长度（SCL-co-MCL）PHA的第一份报告。有趣的是,J9UΔxylD-P8xylA能够有效地利用葡萄糖和木糖作为辅助碳源用于PHA生产。此外，在开放和非无菌条件下，在5-L生物反应器中，与葡萄糖/木糖共补料策略偶联的J9UΔxyD-P8xylA的补料分批发酵达到12.57g/LPHA。J9UΔxylD-P8xylA利用玉米秸秆水解液作为碳源，在开放式发酵中达到7.0g/L细胞干重（CDW）和2.45g/LPHA。总之,与廉价原料相结合的非无菌生产凸显了工程菌株从富含木质纤维素的农业废物中低成本生产PHA的潜力。
