Journal Article

Bacillus aryabhattai TFG5-mediated synthesis of humic substances from coir pith wastes

Uthandi, Sivakumar, Shameer, Syed, Ramachandran, Priyadharshini, Muniraj, Iniyakumar

2021

Overview

Background Humic substances (HS) form the largest proportion among all the constituents of soil organic matter and are a key component of the terrestrial ecosystem. HS plays a multifunctional role in the environment by controlling the biogeochemical carbon cycle, providing nutrients and bio-stimulants for plant growth, and interacting with inorganic and organic pollutants. The rate of formation of HS in soils determines its productivity and carbon sequestration capacity. Enhancement of HS synthesis in the soil through the microbial route not only increases CO 2 sequestration but also mitigates the greenhouse gas emissions in the environment. Result In this study, we attempted to understand the mechanism of formation and enhancement of HS from coir pith wastes using the tyrosinase produced by Bacillus aryabhattai TFG5. The bacterium TFG5 isolated from the termite garden produced the tyrosinase (1.34 U mL −1 ) and laccase (2.1 U mL −1 ) at 48 h and 60 h of fermentation, respectively. The extracellular tyrosinase from B. aryabhattai TFG5 was designated as TyrB. Homology modeling of TyrB revealed a structure with a predicted molecular mass of 35.23 kDa and two copper ions in the active center with its conserved residues required for the tyrosinase activity. TyrB efficiently transformed and polymerized standard phenols, such as p -cresol, p -hydroxyl benzoic acid, Levo DOPA, and 2,6 DMP, besides transforming free phenols in coir pith wash water (CWW). Additionally, UV–Vis and FT-IR spectra of the degradation products of the coir pith treated with TyrB revealed the formation of HS within 3 days of incubation. Furthermore, the E472/664 ratio of the degradation products revealed a higher degree of condensation of the aromatic carbons and the presence of more aliphatic structures in the HS. Conclusion The results confirmed the influence of TyrB for the effective synthesis of HS from coir pith wastes. The results of the present study also confirm the recently accepted theory of humification proposed by the International Humic Substances Society.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Agricultural wastes / Applied Microbiology / Bacillus (Bacteria) / Bacillus aryabhattai / Bacillus aryabhattai TFG5 / Benzoic acid / Binding sites / Biodegradation / Biogeochemical cycles / Biotechnology / Carbon content / Carbon cycle / Carbon dioxide / Carbon dioxide fixation / Carbon sequestration / Chemical properties / Chemistry / Chemistry and Materials Science / Coir / Coir pith biomass / Condensates / Cresols / Degradation / Degradation products / Dihydroxyphenylalanine / Emissions / Environmental aspects / Enzymes / Enzymology / Fermentation / Genetic Engineering / Greenhouse gases / Homology / Humic acids / Humic substances / Humic substances synthesis / Humification / Industrial microorganisms / Infrared spectroscopy / Laccase / Lignin / Microbial enzymes / Microbial Genetics and Genomics / Microbial glycobiotechnology / Microbiology / Microorganisms / Molecular structure / Nutrient cycles / Nutrients / Organic compounds / Organic matter / Oxidative polymerization / Phenols / Physiological aspects / Plant growth / Pollutants / Polymerization / Production processes / Productivity / Proteins / Soil organic matter / Soil pollution / Soils / Stimulants / Synthesis / Tyrosinase / Wash water / Wastes