Capability of the Microalga Scenedesmus dimorphus for Biodegradation of Crude Oil Components: Biological Responses and Catabolic Intermediates

چکیده مقاله

The capability of Scenedesmus dimorphus for biodegradation of crude oil components was evaluated using
biological and biochemical techniques. After exposure of the algal cells to different concentrations of crude oil
for a period of 21 days, growth parameters such as cell number as well as fresh and dry weights have increased
(~twofold) at low concentrations of crude oil (up to 0.04%) in comparison with control samples. However,
growth criteria have decreased in response to the increase in crude oil concentration (0.08--1%). Similar trends
were observed in the content of chlorophylls, carotenoids, flavonoids, anthocyanins and phenols. Crude oil
treatment induced the production of H2O2 (~eightfold) and thiobarbituric acid reacting substance (TBARS)
(>fourfold). As a consequence, enhancing crude oil concentration resulted in increasing activities of superoxide
dismutase (SOD), polyphenol oxidase (PPO), peroxidase (POD) and lipoxygenase (LOX). In comparison, the
activities of catalase (CAT), ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) have
increased at low concentrations (up to 0.02%) and then decreased. Using GC-MS analysis several
biodegradation intermediate compounds were recognized in the culture media over treatment time. Altogether,
growth indices of S. dimorphus have been diminished by crude oil contamination in a dose-dependent manner.
However, this microalgal species showed considerable potential for biodegradation of crude oil components
particularly at concentrations lower than 0.08%. Thus, S. dimorphus could be used as a competent
phytoplankton in removal of crude oil from contaminated water supplies.