Application of Potent Actinomycete Strains for Bio-Degradation of Domestic Agro-Waste by Composting and Treatment of Pulp-Paper Mill Effluent

Abstract

Actinomycetes are known to produce an extensive range of bioactive compounds as well as variety of enzymes having multiple biotechnological applications. They are an important source of lignocellulose hydrolyzing enzymes and constitute considerable proportion of the soil or aquatic micro-flora responsible for degradation of biomass in natural environment. Presently, most of the commercially exploited lignocellulases and commercial biodegradation processes rely mostly on fungal or bacterial micro-organisms. Actinomycetes are relatively less explored for biodegradation processes that utilize lignocellulases for solid agro-waste management and waste water treatment. There is also a need to search and explore novel actinomycete strains for various biodegradation applications. This study involved examining the possibility of using only potent actinomycetes strains for the composting process by creating the consortium of such strains that could produce thermo-tolerant and alkali-tolerant key enzymes necessary for the degradation of cellulose, hemi-cellulose and lignin. The newly developed actinomycete consortium was tested for the composting activity and the composting process was optimized. The analysis of the composted material generated under ideal condition, demonstrated desirable physical and chemical characteristics. Paper pulp effluent poses a hazard to waterways due to toxicity. The toxicity of this mill effluent can be attributed to a compound called lignin and its chlorinated derivatives that are let out during the treatment of lignocellulosic constituents. Current study also involves the use of a strain of actinomycete having ability to produce enzyme laccase, which is active under alkaline condition for the treatment of paper pulp effluent. Enzyme laccase is known for its ability to attack phenolic components of lignin and common hazardous component of effluent, polycyclic aromatic hydrocarbons (PAH). Aerobic treatment of effluent by actinomycete strain indicated 21% reduction in COD at pH 7.5 after 14 days under optimum condition. This strain was identified as Streptomyces rochei based on molecular fingerprinting and was reported to be the producer of laccase probably for the first time. LCMS analysis of the treated effluent sample showed the presence of degradation compounds forming after 7 and 14 days of treatment. These compounds showed the degradation of lignin components and other phenolic, non-phenolic components of the effluent by intra molecular re-arrangement, oxidation and ring opening reactions. Overall, potent thermo-tolerant and alkali-tolerant actinomycete strains were successfully isolated and applied for bio-degradation of domestic agro-waste by composting and treatment of pulp-paper mill effluent. The consortium of these strains may be further utilized for scale-up studies in order to assess its commercial feasibility for biodegradation processes.