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

Abstract

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 CO2 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.

Tyrosinase and laccase-producing Bacillus aryabhattai TFG5 and its role in the polymerization of phenols

“…More importantly, research on such bacteria can unravel the mechanistic role of enzyme-mediated synthesis of HS in the soil so that the synthesis rate of humic substances could be increased, thereby increasing soil carbon sequestration. Previously, we attempted to understand the mechanism of formation and enhancement of HS from coir pith wastes using a tyrosinase produced by B. aryabhattai TFG5 [20]. The present study confirmed the identity of the potential soil bacteria that possess laccase and tyrosinase activity besides characterizing their role in the polymerization of phenols.…”

“…The polymerization of phenolic molecules is vital for the removal of excess phenolic contaminants in wastewater [21], while the polymerization of degraded lignin with amino acids enhances the decomposition process and the formation of soil humic substances [17,27]. In an earlier study, tyrosinase-mediated humification of coirpith wastes was successfully achieved by extracellular protein from B. aryabhattai TFG-5 [20]. The extracellular enzyme was characterized using homology modeling and confirmed as a tyrosinase.…”

“…Besides transforming standard phenols, the extracellular enzyme also transformed free phenols in coirpith wash water. Coirpith wastes when treated with the enzyme synthesized humic substances in a short time [20]. The polymerization of phenols also assists in dye removal and the antioxidant activity of human cells [28].…”

Special Issue ‘Microbial glycobiotechnology’

“…Microbial glycobiotechnology refers to sustainable bioprocesses for the bioconversion of carbohydrates through microbial enzymes and microbial technologies and the generation of tailor-made carbohydrate bioproducts/polymers for various novel applications in bioenergy and bioenergy fuels, biomaterials, in food and nutrition, and pharmaceuticals.This special issue is intended to present a special collection with a thematic scheme: Microbial Glycobiotechnology. Eighteen articles, connected to glycan biosynthesis, glycoenzymology, modification of complex carbohydrates and their corresponding glycoconjugates, including glycans, glycoproteins, glycolipids, biological functions of glycoconjugates and glycolipids, have been published there [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Agriculture Waste Management - A Case study on Bowenpally Mandi

“…Laccases have also been used in the delignification of pulp, bleaching of textiles and carcinogenic dyes, detoxification of water and soils, removal of phenolics from wines, improving adhesive properties of lignocellulosic products, determination of bilirubin levels in serum, and transformation of antibiotics and steroids (Dougherty et al, 2012;Sakurai and Kataoka, 2007). Furthermore, tyrosinase and laccaseproducing Bacillus aryabhattai TFG5 known to enhance the synthesis of humic substances from coir pith waste (Muniraj et al, 2021a;2021b). In addition, laccases have demonstrated potential for use in biosensors, bioreactors, and biofuel cells (Shleev et al, 2005).…”