Bench-scale production of enzymes from the hydrocarbonoclastic bacteria Alcanivorax borkumensis and biodegradation tests

Abstract

This study investigates motor oil (3, 5, 7.5 and 10% (v v−1)) as a sole carbon source for the production of Alcanivorax borkumensis in shake flasks and a 5 L bench-scale fermenter in comparison to the standard media. Shake flask studies showed a significant and higher cell growth (p=0.000038), lipase (p = 0.006900) and alkane hydroxylase production (p = 0.000921) by Alcanivorax borkumensis when motor oil was used as the substrate. Based on Tukey post-hoc tests, 5% motor oil concentration was selected as the optimal substrate concentration. The 5 L fermenter experiments conducted using motor oil at 5% (v v−1) concentration, under controlled conditions exhibited significant and higher alkane hydroxylase and lipase activities (55.6 U mL−1 (p = 0.018418) and 208.30 U mL−1 (p = 0.020087), respectively) as compared with those of motor oil at 3% (v v−1) and n-hexadecane at 3% (v v−1) concentration which was used as control. Cell growth was significantly higher when motor oil (3 or 5%) was used as a substrate (p = 0.024705).Enzymatic degradation tested on two different polycyclic aromatic hydrocarbons (PAHs) contaminated groundwaters showed 37.4% removal after 5 days with a degradation rate of 196.6 ppb day−1 and 82.8% removal after 10 days with a degradation rate of 217.54 ppb day-1 for the 1st site and an almost complete biodegradation with 95% removal and 499.02 ppb day−1 removal rate after only 5 days for the 2nd site.