Formulation of Microbial Consortium for Btex Biodegradation

Karthiga Nagarajan and Kai-Chee Loh. Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117576, Singapore

The mono-aromatic group of hydrocarbons, namely, Benzene, Toluene, Ethyl Benzene and o-Xylene (BTEX) are the most commonly cited environmental pollutants. Though natural ecosystems have self purification capacities, it is essential to adopt proper treatment methodologies to control their discharge into the natural environment. The conventional physico-chemical treatment methods for BTEX are neither cost effective nor easy to operate and also cause secondary pollution problems. Biodegradation, on the other hand, emanates as a promising approach for the removal of BTEX from industrial effluents.

In this research, we aimed at developing a concoction of two bacterial cultures, Pseudomonas putida F1 and Pseudomonas stutzeri OX1, for the effective biodegradation of BTEX compounds. It is anticipated that mixed cultures will perform better than single cultures. Pure substrate and mixed substrate studies conducted to elucidate the biodegradation capacities of each species showed that the biodegradation capability of the species complemented each other synergistically.

Based on the biodegradation profiles of the pure cultures, a number of parameters were chosen as heuristics to mix the bacteria depending on the effluent BTEX composition. The heuristics were used to formulate mixed microbial consortium for three different concentration levels of BTEX compounds. The mixed community of the two species demonstrated better biodegradation capability than the individual pure culture. It was found that the initial inoculum size and proportion of both the species in the consortium played a significant role in improving the efficiency of BTEX removal.

A novel genome based methodology was developed to differentiate and characterize the two species in the constructed consortium. This methodology helped in optimizing the species proportions based on the population stability during biodegradation. The methodology also threw light on understanding the population dynamics of the mixed culture, microbial interactions, and biodegradation capacity of each species in the mixed substrate system.