嗜鹽菌Haloferax mediterranei PHA生合成之探討

This study is focus on the variation of activities for PHA synthase and PHA depolymerase as well as the PHA biosynthesis in the fermentation of haliphilic Haloferax mediterranei. H. mediterranei was cultured in shacking culture with the glucose, extructed bran/starch, or n-butanic acid as carbon sources. Above 0.1 % n-butanic acid would inhibited the growth of H. mediterranei. The extructed bran/starch was the most favorable carbon source for this bacterial growth and it had higher activity of PHA synthase but lower of PHA depolymerase. In the fermentation of continuous feeding-batch controlled by pH-stat, the activity curves for PHA synthase and PHA depolymerase were similar to the growth curve but delayed for a few hours. Using liquid culture as starter for the fermentation of continuous feeding- batch, it took 50 hrs to the maximum of cell dry weight and was only the half of time by using the suspension of colony from plate. It also had higher activity of PHA synthase than activity of PHA depolymerase. However, the CDW, PHA amount, and PHA content were lower. It showed that the biosynthesis of PHA was related to the bacterial physiologic state and PHA-related enzymes were expressed at late exponential phase. It was failure to merge the peptide sequences of PHB granule bound proteins obtained from the sequencing results by Q-TOF. The PHB relative enzymes had been partially purified, but the recovery of these enzymes activities were very low after ultracentrifugaion due to their unstability in purification procedure. It is necessary to study the enzyme stability in future.