Bacterial laccases: some recent advances and applications

Laccases belong to the large family of multi-copper oxidases (MCOs) that couple the one-electron oxidation of substrates with the four-electron reduction of molecular oxygen to water. Because of their high relative non-specific oxidation capacity particularly on phenols and aromatic amines as well as the lack of requirement for expensive organic cofactors, they have found application in a large number of biotechnological fields. The vast majority of studies and applications were performed using fungal laccases, but bacterial laccases show interesting properties such as optimal temperature above 50 °C, optimal pH at the neutral to alkaline range, thermal and chemical stability and increased salt tolerance. Additionally, bacterial systems benefit from a wide range of molecular biology tools that facilitates their engineering and achievement of high yields of protein production and set-up of cost-effective bioprocesses. In this review we will provide up-to-date information on the distribution and putative physiological role of bacterial laccases and highlight their distinctive structural and biochemical properties, discuss the key role of copper in the biochemical properties, discuss thermostability determinants and, finally, review biotechnological applications with a focus on catalytic mechanisms on phenolics and aromatic amines.info:eu-repo/semantics/publishedVersio

Calcite dissolution by <em>Bacillus subtilis</em> SSRCI02: An <em>in vitro</em> study for the reclamation of calcareous saline-sodic soils

1267-1273Dissolution of calcite by microorganisms to supply Ca2+ to replace Na+ in soil exchange sites is an important trait to reduce salinity and sodicity. An attempt was made to isolate and screen calcite dissolving bacteria for reclamation of calcareous saline-sodic soils and also to promote better crop growth. While screening the isolates for calcite solubilization index (0.37 to 2.62) and titratable acidity (0.04 to 0.25 g.l-1), the isolate SSRCI02 possessing higher dissolution was identified as Bacillus subtilis. Acetic and gluconic acid produced by B. subtilis SSRCI02 in the presence of CaCO3 recorded 20% of calcite dissolution with release of sufficient Ca2+ ions. Further, FT-IR spectra confirmed reduction of native calcite (69.1 to 62.5) suggesting their dissolution. Siderophore and extracellular polysaccharide productions might also aid in calcite dissolution and plant growth promotion as evidenced by indole acetic acid production, P and Zn solubilization

Gibberellic acid production by <i>Fusarium fujikuroi </i>SG2

211-214Present study isolates efficient strains of gibberellins producing fungal strains from ‘bakanae’ diseased root system of rice plants for their GA3 production potentials in Czapek-Dox liquid medium/improved medium. One of the isolates SG2 (GA3, 1175 mg/l) produced higher GA3 than standards strains of Gibberella fujikuroi, which was identified as Fusarium fujikuroi SG2 (MTCC4649). While studying GA3 production pattern by this strain, gibberellin synthesis initiated on 3rd day and reached maximum by 9th day of fermentation

EnZolv delignification of cotton spinning mill waste and optimization of process parameters using response surface methodology (RSM)

Abstract Background EnZolv is a novel enzyme-based, eco-friendly biomass pretreatment process that has shown great potential in the field of textile engineering and biotechnology. It employs laccase from Hexagonia hirta MSF2 and 2% ethanol in the process of delignification. The process is designed to evaluate optimal conditions to remove lignin and other impurities from cotton spinning mill waste (CSMW), without compromising the quality and strength of the fibers. CSMW is a low-cost and readily available source of cellulose, making it an ideal candidate for delignification using EnZolv. By optimizing the pretreatment conditions and harnessing the potential of enzymatic delignification, this research aims to contribute to more sustainable and efficient ways of utilizing lignocellulosic biomass in various industries for the production of biochemical and bioproducts. Results The present study emphasizes the EnZolv pretreatment in the delignification of cotton spinning mill wastes irrespective of the cellulose content. EnZolv process parameters such as, moisture content, enzyme load, incubation time, incubation temperature, and shaking speed were optimized. Under pre-optimized conditions, the percent lignin reduction was 61.34%, 61.64%, 41.85%, 35.34%, and 35.83% in blowroom droppings (BD), flat strips (FS), lickerin fly (LF), microdust (MD) and comber noils (CN), respectively. Using response surface methodology (RSM), the statistically optimized EnZolv pretreatment conditions showed lignin reduction of 59.16%, 62.88%, 48.26%, 34.64%, and 45.99% in BD, FS, LF, MD, and CN, respectively. Conclusion Traditional chemical-based pretreatment methods often involve harsh chemicals and high energy consumption, which can have detrimental effects on the environment. In contrast, EnZolv offers a greener approach by utilizing enzymes that are biodegradable and more environmentally friendly. The resulting fibers from EnZolv treatment exhibit improved properties that make them suitable for various applications. Some of the key properties include enhanced cellulose recovery, reduced lignin content, and improved biophysical and structural characteristics. These improvements can contribute to the fiber's performance and processability in different industries and future thrust for the production of cellulose-derived and lignin-derived bioproducts. Graphical Abstrac

Activity and Transcriptional Regulation of Bacterial Protein-Like Glycerol-3-Phosphate Dehydrogenase of the Haloarchaea in Haloferax volcanii▿†

Glycerol is a primary energy source for heterotrophic haloarchaea and a major component of “salty” biodiesel waste. Glycerol is catabolized solely by glycerol kinase (encoded by glpK) to glycerol-3-phosphate (G3P) in Haloferax volcanii. Here we characterized the next critical step of this metabolic pathway: the conversion of G3P to dihydroxyacetone phosphate by G3P dehydrogenase (G3PDH). H. volcaniiharbors two putative G3PDH operons: (i) glpA1B1C1, located on the chromosome within the neighborhood of glpK, and (ii) glpA2B2C2, on megaplasmid pHV4. Analysis of knockout strains revealed that glpA1(and not glpA2) is required for growth on glycerol. However, both glpA1and glpA2could complement a glpA1knockout strain (when expressed from a strong promoter in trans) and were required for the total G3PDH activity of cell lysates. The glpA1B1C1, glpK, glpF(encoding a putative glycerol facilitator), and ptsH2(encoding a homolog of the bacterial phosphotransferase system protein Hpr) genes were transcriptionally linked and appeared to be under the control of a strong, G3P-inducible promoter upstream of glpA1. Overall, this study provides fundamental insights into glycerol metabolism in H. volcaniiand enhances our understanding of central metabolic pathways of haloarchaea