A viable antibiotic strategy against microbial contamination in biotechnological production of polyhydroxyalkanoates from surplus whey

The study demonstrates the successful application of vancomycin for inhibiting growth of the contaminant Bacillus cereus in a polyhydroxyalkanoate (PHA) production process with Hydrogenophaga pseudoflava on whey. The minimum inhibiting concentration (MIC) of vancomycin for both strains was calculated in minimal medium H3 as well as in H3 medium supplemented with yeast extract. MIC for B. cereus was 0.57 μg mL−1 and 1.63 μg mL−1 in H3 and H3 plus yeast extract respectively. For H. pseudoflava, MIC amounted to 2.8 μg mL−1 in H3 medium and 6.88 μg mL−1 in H3 plus yeast extract. The effect of vancomycin on PHA production was minimal or negligible up to a vancomycin concentration of 1 μg mL−1 in both media. The specific PHA production rates of H. pseudoflava decreased with increasing antibiotics in a minimal medium but in media supplemented with yeast extract the specific PHB production rates increased as the antibiotics concentrations increased.