Production of poly-Β-hydroxybutyrate in the Azotobacteraceae
The production of poly-(beta)-hydroxybutyrate (PHB) in the Azotobacteraceae has been investigated. It has been demonstrated that nitrogen fixation is unnecessary for PHB accumulation in the Azotobacteraceae. PHB is produced in a mineral-salts medium containing glucose and fixed nitrogen in the form of potassium nitrate. PHB is accumulated in equivalent levels in media with or without nitrate. However, total cell mass is higher when nitrate is supplied. Nitrogenase defective mutants of Azotobacter do not accumulate PHB;Azotobacter cells also encyst in the presence of nitrate when glucose is limited. Thus, nitrogen limitation is not a precondition for encystment as previously believed. Carbohydrates and reduced nitrogen must be limited in order for encystment to occur. PHB accumulation may be a precondition of encystment;A method for the production of PHB from Azotobacter which allows the isolation of more PHB per unit of production media than other published methods has been determined. This fermentation proceeds at higher temperatures than usually reported for Azotobacter (33-35(DEGREES)C). Phenylacetic acid supplements do not result in increased yields of either cell mass or PHB;A new and superior stain for PHB, based on the fluorescent staining of the polymer with Nile Blue Sulfate, has been developed. Colony replicas on glass-fiber filters also stain with Nile Blue, allowing the rapid screening of isolates for PHB production.