Abstract

A microbial medium, designated DYSP medium, was produced from food wastes that included defatted soya, clear beer spent yeast, potato solid waste and opaque beer spent grains. Various combinations of the food wastes were used for the media formulations and evaluated for extent of supporting microbial growth of pure cultures. A 3.0 M sodium hydroxide hydrolysis followed by a neutralization process using concentrated hydrochloric acid has been established and standardized for the preparation of the medium. A dry pulverized medium was produced that could be reconstituted in distilled water (dH₂O) without settleable solids.The formulated DYSP medium supported the growth of Escherichia coli, Bacillus subtilis,Bacillus cereus, Staphylococcus aureus, Aspergillus niger and Saccharomyces cerevisiae. The composition of the medium was 35.45% protein, 5.7% nitrogen, 56.6% ash, 8.6% moisture and 0.012 mg/ml of total reducing sugar. The pH of the DYSP broth was 6.6 when reconstituted in distilled water. Traditional classical microbiological studies demonstrated that the test cultures could grow and retain normal phenotypic and morphological properties when cultured on the formulated medium.The DYSP medium containing ampicillin, isopropyl ß-D-1-thiogalactopyranoside and 5-bromo-4-chloro-3-indolyl-ß-D-galactoside proved to be an equally alternative medium in molecular biology for selection and screening E. coli TG1 cells transformed with pUC18 plasmid. Other preliminary biotechnological results showed that the formulated medium could form a base for studying and optimizing the production of penicillin byP. chrysogenum.

Key words: Food wastes, chemical hydrolysis culturing medium, fermentation and molecular biology.