Polyhydroxyalkanoates in Gram-positive bacteria: insights from the genera Bacillus and Streptomyces

Gram-positive bacteria, notably Bacillus and Streptomyces, have been used extensively in industry. However, these microorganisms have not yet been exploited for the production of the biodegradable polymers, polyhydroxyalkanoates (PHAs). Although PHAs have many potential applications, the cost of production means that medical applications are currently the main area of use. Gram-negative bacteria, currently the only commercial source of PHAs, have lipopolysaccharides (LPS) which co-purify with the PHAs and cause immunogenic reactions. On the other hand, Gram-positive bacteria lack LPS, a positive feature which justifies intensive investigation into their production of PHAs. This review summarizes currently available knowledge on PHA production by Gram-positive bacteria especially Bacillus and Streptomyces. We hope that this will form the basis of further research into developing either or both as a source of PHAs for medical applications.