Investigation of the effects of the types of food waste utilized as carbon source on the molecular weight distributions and thermal properties of polyhydroxy-butyrate produced by two strains of microorganisms

The average molecular weight and molecular weight distribution of poly-hydroxybutyrate can be affected by different bacterial strains, different cultivation time and also different carbon sources. Food waste was proven to have a high potential in the induction of biosynthesis of polyhydroxybutyrate with different production yields and physical properties. A specific culture of Alcaligenes latus DSM 1124 and Staphylococcus epidermidis, which was isolated from sesame oil, were selected to ferment several types of food wastes as nutrients, including malt waste, soy waste, confectionery waste, milk waste, vinegar waste and sesame oil, into polyhydroxybutyrate in this study. Average molecular weight and molecular weight distribution of polyhydroxybutyrate were measured by gel permeation chromatography. By comparing the results with those obtained using sucrose as a carbon source, the average molecular weight of polyhydroxybutyrate produced from food wastes was increased for Alcaligenes latus; however, it was decreased for S. epidermidis. Thermal analyses of the biopolymer produced by S. epidermidis indicated that the melting point of the polymer produced from sesame oil as carbon source was 188°C, the highest temperature among those polymers produced by using ice cream, malt, and soya wastes.