Antibiotic-Producing Streptomyces griseus and Biodiesel Glycerol Byproduct in Undergraduate Research

Graves, James, Kyle Carrizales, and Ali Zeitoun

Actinomycete isolation agar (AIA) and glycerol yeast extract agar (GYEA) are used for recovery and growth of Actinomycetes and contain glycerol. This work examined growth and antimicrobial activity of Streptomyces griseus on media prepared with biodiesel glycerol byproduct made by transesterification or catalyst column. On AIA, S. griseus and Pseudomonas aeruginosa would grow, but not Staphylococcus epidermidis, Streptococcus faecalis, Escherichia coli, Klebsiella pneumoniae and Serratia marcescens. On minimal agar, containing only essential nutrients, with glucose, glycerol or glycerol byproducts as carbon sources, S. griseus, E. coli, K. pneumoniae, P. aeruginosa and S. marcescens exhibited growth, but not S. epidermidis and S. faecalis. All the bacteria grew on yeast extract agar (YEA), without or with addition of glucose, glycerol, or glycerol byproducts. Antibiograms made by the disk diffusion technique indicated that E. coli, K. pneumoniae, P. aeruginosa and S. marcescens were sensitive to streptomycin, but S. epidermidis and S. faecalis showed resistance. S. griseus inhibition of antibiotic sensitive E. coli growth was detected by a cross-streak inoculation test which included additional streak inoculations of E. coli on subsequent days. S. griseus did not produce enough antibiotic to inhibit sensitive bacteria inoculated on the same day. Inhibition of E. coli growth was observed on minimal agar containing glycerol, glycerol byproduct made by catalyst column, and other added carbon sources tested by 7, 9 and 14 days respectively. Inhibition of growth of E. coli occurred on YEA with all added carbon sources tested by three days incubation of S. griseus. Distance of growth inhibition from S. griseus increased with incubation period. Byproduct from catalyst column produced the most rapid increase in distance of inhibition. Factors associated with production of antimicrobial may be complex. These findings suggested that biodiesel glycerol byproduct can be used in media where a product is synthesized.