4 research outputs found

    Laccase production by selected bacteria species isolated from some aquatic and terrestrial milieu of the Eastern Cape : applications in wastewater treatment

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    Aromatic pollutants are a diverse group of chemicals which are continuously produced from industrialization, urbanization and sophistication in technological advancement. Pristine water source polluted by these chemicls makes the water unsafe for human consumption, and as well disrupts the trophic structure of the aquatic milieu. Physico-chemical treatment techniques employed so far have been accompanied by major drawbacks which have overriden the relative successes recorded, hence, greener, simpler and more efficient methods of pollutant transformation is imperative. The prospect of enzymatic treatment of pollutants has gradually been receiving growing attention in contemporary times due to the their environmental friendliness and production economic feasiblity. Laccase, a multicopper oxidase has heightened its appeal towards environmental and biotechnological applications due to its broad substrate specificity and its requirement of atmospheric molecular oxygen as a cosubstrate and the discharge of water as the byproduct. Hence, this present study was designed to evaluate the biotechnological potentials of laccases produced by some bacteria species from some aquatic biomes of the Eastern Cape Province, South Africa. The laccase-producing bacteria were isolated from selected environmental samples by selective enrichment using selective aromatic compounds as sole carbon source and subsequently, laccase-screening phenolic substrates. The laccase-producing bacteria were identified by molecular techniques as proteobacteria belonging to the following genera: Achromobacter, Bordetella, Citrobacter, Pseudomonas and Stenotrophomonas. Optimisation of laccase production in a submerged fermentation was by traditional and statistical methods, where four isolates (Hb9c; Achromobacter xylosoxidans HWN16, Hb16c; Bordetella bronchisepta HSO16, Berl11b2; Stenotrophomonas maltophilia BIJ16, Ie1c; Citrobacter freundii LLJ16) were evaluated for the fermentative production of laccase from lignocellulosic agroindustrial residues. Predictions from statistical optimisation showed that weakly acidic conditions (pH 5) and low agitation speed (100 rpm) were required for maximum laccase production from mandarin peelings (0.5 g/200 mL) and NaNO3 (0.25 g/200 mL) in Hb9c, maize stover (0.50 g/200 mL) and NaNO3 (0.050 g/200mL) in Berl11b2 while a lower agitation speed (50 rpm) was required for maximum laccase output from 2.0 g/200 mL maize stover and 0.050 g/200 mL KNO3 in Ie1c. However, 2.50 g/200 mL wheat bran, 0.050 g/200 mL yeast extract and 50 rpm agitiation under acidic conditions (pH3) yielded maximum laccase titres in Hb16c. Further characterisation of Hb9c and Ie1c laccase secretions portrayed their polyextremotolerant capacities. They were active at a broad range of tempertaure (0-90 degreesC); with optima at 70°C (Hb9c) and 60°C (Ie1c), pH (3-11); with optima at pH 6 (Ie1c) and pH 8 (Hb9c), respectively, and were equally thermo- and pH-stable. Their activities were either improved or left unabated by high concentrations of cations, detergents, and chloride. In addition, catalytic activities of Hb9c and Ie1c laccase secretions increased when they were preincubated with 2 – 20 percent of fluoride, a potent inhibitor. Consequently, a molecular perspective depicted the isolates to have multiple homologous laccase encoding genes. The enzymes were successfully immobilised on solid supports comprising gelatin and Na-alginate with a recovery of cca. 85 percent residual activity after 8 cycles of oprertional stability experiments. The immobilised laccases were remarkable in the decolourisation of synthetic dyes, albeit, free forms also elicited satisfactory performances. Ultimately, the application of free laccases in denim bleaching, individually or with a blend of a mediator, ABTS, showed that denim colours could be bleached without the need for chemical bleaching agents. The results obtained suggest the bacteria laccases produced from lignocellulosic wastes may serve as potent degraders of phenolic pollutants in water and, may also contribute to the bioeconomy and promote greener techniques for industrial applications

    Optimization and Characterization of Tyrosinases from Multi-enzyme Producing Fusarium solani and Fumago sp.

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    Tyrosinase is a copper-containing metalloprotein that catalyzes the oxidation of tyrosine, in particular, L-DOPA to L-Dopaquinone, which are precursors of brown pigments in some wounded eukaryotic tissues. The present study focused on screening, production and characterization of tyrosinase from multi-enzyme producing Fusarium solani B1 and Fumago sp. A total of 25 strains were isolated from rotting wood samples and screened for hydrolytic and oxidative multi-enzyme potentials using different polymeric substrates. The two most consistent strains: Fusarium solani B1 and Fumago sp. B13 were further evaluated for tyrosinase production. Some media cultural parameters and physiological conditions were optimized in order to maximize tyrosinase production. Incubation of Fumago sp. B13 and Fusarium solani B1 for 96 and 144 h in medium containing 2 % and 0.2 % ratios of Glucose and NaNO3 with pH 6 and 7, respectively, was most suitable for tyrosinase production. Characterization of the partially purified tyrosinase from Fumago sp. B13 and Fusarium solani B1 exhibited optimal activities at pH 6-7, 30 °C, and 1 mM Cu2+, respectively, thereby suggesting their potentials for novel biotechnological applications

    The Sustainable Production of a Novel Laccase from Wheat Bran by Bordetella sp. JWO16: Toward a Total Environment

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    Laccase is increasingly adopted in diverse industrial and environmental applications, due to its readily accessible requirements for efficient catalytic synthesis and biotransformation of chemicals. However, it is perceived that its industrial production might incur some unfavorable overhead, which leads to expensive market products, and the corresponding negative environmental feedback, due to the use of capital-intensive and precarious chemicals. To this end, this study was designed to evaluate the performance indicators of the valorization of wheat bran by a novel Jb1b laccase and its subsequent application in waste minimization and water management, on a laboratory scale. Optimal Jb1b laccase was produced in submerged fermentation medium containing wheat bran, an agroindustrial residue, through response surface methodology (RSM) algorithm, and was applied in dye decolorization and denim bioscouring, respectively. Results showed that the resultant enzyme manifested unique biochemical properties, such as enhanced tolerance at certain physicochemical conditions, with a residual activity of at least ca. 76%. Furthermore, phenomenally high concentrations of synthetic dyes (0.2% w v−1) were decolorized over 56 h, and a 6 h mediator-supported simultaneous denim bleaching and decolorization of wash effluent was observed. The sustainability of the production and application processes were inferred from the reusability of the fermentation sludge as a potential biofertilizer, with subsequent prospects for the biostimulation and bioaugmentation of contaminated soils, whereas the decolorized water could be adopted for other uses, amongst which horticulture and forestry are typical examples. These phenomena therefore authenticate the favorable environmental feedbacks and overhead realized in this present study

    Effect of different milk based media on lactic acid production and growth characteristics of bacteria isolates from vended soft cheese

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    455-459Lactic acid production has been traditionally practiced by locals worldwide for centuries. The discovery of its relevance in various industries, particularly the food industry, and in biopolymer production, has called for its economic production from suitable, cheap feedstocks like agroindustrial byproducts. This study, therefore, investigated the growth and lactic acid production patterns of some lactic acid bacteria (LAB) isolated from a named west African fermented food (Wara) in different dairy media. The study was conducted using submerged fermentation, where whole milk, skim milk medium, cheese whey and non fat milk were assessed as suitable substrates, with respect to the varying temperature regimes (30, 37 and 42°C), over 48 h. The results revealed that (i) milk remains a vital source for lactic acid bacteria; (ii) medium components and environmental conditions are contributory in growth and lactic acid production of lactic acid bacteria in the different media; (iii) the active growth might not necessarily depict increased lactate production; (iv) the species of a genus might show similar population dynamics and physiological characteristics depending on the environment they exist; and (v) the dairy waste should be incorporated in large scale lactic acid production to improve the biomass yield
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