Effect of cosubstrates on primary biodegradation of triphenylmethane dyes by Pseudomonas sp.

Abstract

The effect of substrates (glucose, starch, lactose and sucrose) on primary biodegradation (decolourisation) of recalcitrant triphenylmethane dyes Brilliant green and Crystal violet) by Pseudomonas sp was investigated. Biodegradation was enhanced in cultures with substrate supplementation. Glucose and starch were the best among the substrates tested. The percentage decolourisation increased with increasing concentration up to maximum of 0.2mgL-1 for glucose and 0.3mgL-1 for starch. The percentage with glucose was 93.30 ± 1.40% for Brilliant green and 90.20± 0.75% for Crystal violet. With 0.30 mgL-1 of starch the percentage decolourisation was 85.30± 0.180% for Brilliant green and 88.50± 0.90% for Crystal violet. Enhanced biodegradation was attributed to generation of redox equivalent (electron donors) as a result of metabolism of glucose and starch as cosubstrates. Decrease in percentage decolorisation at concentration above the maximum for glucose and starch was attributed to saturation of the binding; sites for redox equivalents to the chromophoric group (of quinone) of the dyes and/or metabolite repression of the peroxidase enzyme that catalyses the reductive cleavage of the chromophoric group. Cassava peeling (an agricultural waste) gave values of percentage decolourisation of 63± 0.8% for Brilliant green and 67.70± 0.60% for Crystal violet. The potential of agricultural wastes to enhance primary biodegradation of recalcitrant synthetic dyes is also revealed in this work.


Keywords: Pseudomonas sp., Triphenylmethane dyes, primary biodegradation, cosubstrates

AJAZEB Vol. 7 2005: pp. 38-44