Unsterile and continuous production of polyhydroxybutyrate by Halomonas TD01

► We isolate a moderate halophile Halomonas TD01 from environmental samples. ► This strain could reach high cell density containing amounts of PHA in MM-G medium. ► An open process without sterilization is feasible based on Halomonas TD01. ► An open and continuous fermentation process has been developed. An unsterile and continuous fermentation process was developed based on a halophilic bacterium termed Halomonas TD01 isolated from a salt lake in Xinjiang, China. The strain reached 80g/L cell dry weight containing 80% poly(3-hydroxybutyrate) (PHB) on glucose salt medium during a 56h fed-batch process. In a 14-day open unsterile and continuous process, the cells grew to an average of 40g/L cell dry weight containing 60% PHB in the first fermentor with glucose salt medium. Continuous pumping of cultures from the first fermentor to the second fermentor containing the nitrogen-deficient glucose salt medium diluted the cells but allowed them to maintain a PHB level of between 65% and 70% of cell dry weight. Glucose to PHB conversions were between 20% and 30% in the first fermentor and above 50% in the second one. This unsterile and continuous fermentation process opens a new area for reducing the cost in polyhydroxyalkanoates production.