Establishment of low‐cost production platforms of polyhydroxyalkanoate bioplastics from Halomonas cupida J9

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 J9UΔ xylD ‐P8 xylA 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, J9UΔ xylD ‐P8 xylA was capable of efficiently utilizing glucose and xylose as co‐carbon sources for PHA production. Furthermore, fed‐batch fermentation of J9UΔ xylD ‐P8 xylA 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 J9UΔ xylD ‐P8 xylA 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.