The impact of printing industry effluent on the growth and antioxidant response of the freshwater green microalga Chlorella sorokiniana

Abstract

Contamination of aquatic ecosystems with printing industry wastewater is a serious concern because of the toxicity associated with the effluent components and a tendency to create cascading ecological effects. The influence of printing-press effluent on the freshwater microalga Chlorella sorokiniana strain UTEX2714 was studied under controlled laboratory conditions. The microalga was subjected to various effluent concentrations prepared by diluting printing-press effluent with bold basal medium (BBM) in the following ratios (effluent:medium): 1:149, 1:119, 1:99, 5:95 and 10:90, reflecting greater concentrations of the effluent. The control BBM had no effluent added. Higher effluent concentrations had a negative impact on the cell density of C. sorokiniana; at low effluent concentrations the algae displayed a high growth rate and high chlorophyll a production (p < 0.05), although total chlorophyll content did not differ significantly among treatments (p ≥ 0.05). This study also discovered an increase in peroxidase activity in this microalga in response to higher concentrations of printing-press effluent, which indicated an increase in oxidative stress that prompted antioxidant defence mechanisms. We conclude that printing-press effluent adversely affects the physiology of C. sorokiniana, indicating the potential of printing wastewater to harm phytoplankton in freshwater environments.