Optimization and comparative study of Bacillus consortia for cellulolytic potential and cellulase enzyme activity

Lignocellulosic biomass, owing to its recalcitrant nature, requires a consortium of enzymes for its breakdown. The present study deals with the isolation of cellulolytic bacterial strains from landfill leachate collected from the Pulau Burung landfill site of Penang, Malaysia, and consortia were constructed to test their cellulolytic efficiency. The dinitro salicylate method was used for the estimation of enzyme activity, and consortia were compared with promising bacterial strains. The combined potential of promising bacterial strains was optimized at varying experimental conditions to detect their maximum cellulolytic activity. The results showed that eight bacterial strains reflected hydrolytic activities, and these were identified by 16S rDNA sequence as Bacillus subtilis, Bacillus pumilus, Bacillus proteolyticus, Bacillus paramycoides, Bacillus cereus, Bacillus altitudinis, Bacillus niacin, and Bacillus thuringiensis. Consortia A included Bacillus proteolyticus, Bacillus subtilis, Bacillus pumilus, and Bacillus paramycoides and reflected high thermophilic inclination as the optimal temperature was 45°C at pH 6 with the highest cellulase activity of 0.90 U/ml. Consortia B included Bacillus cereus, Bacillus altitudinis, Bacillus niacin, and Bacillus thuringiensis and showed a cellulase activity of 0.78 U/ml at 38°C and pH 6. The results reflected the significant potential of these Bacillus strains and consortia in the breakdown of cellulose into useful end products. The consortia further proved that a synergistic relationship was more favourable for bioconversion processes.