Production and Characterization of Polyhydroxyalkanoates from Lactic Acid Bacteria Isolated from Dairy Wastewater, Fermented Cow Milk and ‘Ogi’

Aims: This study aimed at screening, producing and characterizing polyhydroxyalkanoates (PHA) from lactic acid bacteria (LAB) isolated from dairy wastewater, fermented cow milk and “ogi”.

Place and Duration of Study: Department of Microbiology, Faculty of Science, University of Ibadan, Ibadan between August 2018 and February 2019.

Methodology: The initial screening of isolated LAB was carried out by Sudan Black staining method followed by secondary screening on liquid medium. Isolates that tested positive for Sudan Black stain and had the highest PHA yield from liquid medium was used for further analysis. The cell walls of selected isolates were lysed with sodium hypochlorite and PHA extracted using chloroform. Optimization of PHA production was carried out using different carbon and nitrogen sources, incubation temperature, pH and agitation speed. Extracted PHA was characterized by FTIR spectroscopy and the microstructure and surface morphology were observed using Scanning Electron Microscope.

Results: Seven isolates tested positive for Sudan Black stain of which two isolates identified as Lactobacillus plantarum CW10 and Lactobacillus casei WWD3 had the highest PHA yield from liquid medium. From the optimization experiment, highest PHA production was observed in Lactobacillus plantarum CW10 (20.5%) and Lactobacillus casei WWD3 (19.7%) when glucose and ammonium sulphate was used as carbon and nitrogen sources respectively, and at pH 6, agitation speed of 200 rpm and incubation temperature of 35oC and 40oC. The spectra of extracted PHA as characterized by FTIR showed absorption peaks for the carbonyl, C-H, -OH, aliphatic -CH3 and ester groups that are characteristics of PHA. The microstructure and surface morphology shows grains that are pseudo-spherical in shape with fairly regular distribution.

Conclusion: There is an appreciable production of PHA from the Lactobacillus strains and can be considered as part of the choice of organisms for PHA production in commercial quantity.