Analysis of bacterial growth parttern in bioprocessing of polyhydroxyalkanoates from waste oil by Pseudomonas oleovorans

Pseudomonas oleovorans NCIMB 6576 and Ralstonia eutropha NCIMB 10442 were used for the production of Polyhydroxyalkanoates (PHA) from industrial waste cooking oils, the bacteria were cultured on tryptone soya broth (TSB) and Tryptone soya agar (TSA). The growth pattern of the bacteria, serial dilution and viable counting was done using the Miles and Misra method, 0.5ml (500 µl) of the sample was transferred aseptically into test tubes filled with 4.5ml ringer solution (1/4 strength) resulting in a ten-fold dilution, the growth curve of the cultures of P. oleovorans NCIMB6576 grown on TSB with and without PS oil sample shows error bars in the graph for each point depicting the standard error of the mean. The initial viable count ranges between 6.37 log10 cfu/ml and 5.1 log10 cfu/ml. The viable count reached its peak after 30 hours giving approximately 9.7 log10 cfu/ml for P. oleovorans NCIMB6576 with PS oil and 9.24 log10 cfu/ml after 30 hours as well without the oil, showing that maximum cell count was attained at the same time. The growth curves of P. oleovorans NCIMB6576 grown on TSB with and without the oil sample TS, where the errors bars depicts the standard errors of the means on each point. The initial viable count at the start of the experiments shows that for P. oleovorans NCIMB6576 grown with the oil, there was an initial viable count of 6.1 log10 cfu/ml as compared to 5.1 log10 cfu/ml without the oil respectively. It was observe that the time at which maximum cell counts was attained is slightly longer when the oil was not used as a carbon source (30 hours) as compared to the oil control (27 hours). A decline in cell count is also noticeable after 30 hours until it reaches its minimum value of 9.4 log.10 cfu/ml after 48 hours in the experiment involving the oil sample TS