Poly-3-hydroxybutyrate(PHB)with high purity and high molecular weight is obtained from halophiles fermentation broth by enzymatic digestion method.Cell walls of halophiles are separately broken by heat treatment and muramidase hydrolysis,and then further purified by neutral alkaline protease.Results show that high temperature treatment at 121℃can effectively break the walls of halophile cells,but it also makes the molecular weight of PHB decline by30%-40%.Under the conditions of 50℃and a pH of 6,the addition of 0.3 wt%muramidase for 60 min of enzymatic hydrolysis can receive the best wall-breaking effect,and the decline of PHB molecular weight can be maintained within 10%.Under the conditions of 70℃and a pH of 10,adding 0.045 wt%neutral alkaline protease for 60 min of enzymatic hydrolysis can achieve the best purification effect,the resulted PHB has a purity of higher than 97%.Through comparing with commercially available PHBs,the chemical structure and thermal properties of the resulted PHB are confirmed.Specific enzymatic hydrolysis ensures that PHB structure is not destroyed.Therefore,PHB with high purity and high molecular weight can be obtained by muramidase-neutral alkaline protease enzymatic digestion,which is an efficient and environmentally friendly method without the aid of other chemical reagents.
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