Everton Skoronski

Substrate specificity and enzyme recycling using chitosan immobilized laccase.

The immobilization of laccase (Aspergillus sp.) on chitosan by cross-linking and its application in bioconversion of phenolic compounds in batch reactors were studied. Investigation was performed using laccase immobilized via chemical cross-linking due to the higher enzymatic operational stability of this method as compared to immobilization via physical adsorption. To assess the influence of different substrate functional groups on the enzyme’s catalytic efficiency, substrate specificity was investigated using chitosan-immobilized laccase and eighteen different phenol derivatives. It was observed that 4-nitrophenol was not oxidized, while 2,5-xylenol, 2,6-xylenol, 2,3,5-trimethylphenol, syringaldazine, 2,6-dimetoxyphenol and ethylphenol showed reaction yields up 90% at 40 °C. The kinetic of process, enzyme recyclability and operational stability were studied. In batch reactors, it was not possible to reuse the enzyme when it was applied to syringaldazne bioconversion. However, when the enzyme was applied to bioconversion of 2,6-DMP, the activity was stable for eight reaction batches.

Immobilization of laccase from Aspergillus oryzae on graphene nanosheets

Laccase enzymes of Aspergillus oryzae were immobilized on graphene nanosheets by physical adsorption and covalent bonding. Morphological features of the graphene sheets were characterized via microscopy techniques. The immobilization by adsorption was carried out through contact between graphene and solution of laccase enzyme dissolved in deionized water. The adsorption process followed a Freundlich model, showing no tendency to saturation within the range of values used. The process of immobilization by covalent bonding was carried out by nitration of graphene, followed by reduction of sodium borohydride and crosslinking with glutaraldehyde. The process of immobilization by both techniques increased the pH range of activity of the laccase enzyme compared to the free enzyme and increased its operating temperature. On operational stability, the enzyme quickly loses its activity after the second reaction cycle when immobilized via physical adsorption, while the technique by covalent bonding retained around 80% activity after six cycles.

Beta glucosidase from Bacillus polymyxa is activated by glucose-6-phosphate.

Optimization of cellulose enzymatic hydrolysis is crucial for cost effective bioethanol production from lignocellulosic biomass. Enzymes involved in cellulose hydrolysis are often inhibited by their end-products, cellobiose and glucose. Efforts have been made to produce more efficient enzyme variants that are highly tolerant to product accumulation; however, further improvements are still necessary. Based on an alternative approach we initially investigated whether recently formed glucose could be phosphorylated into glucose-6-phosphate to circumvent glucose accumulation and avoid inhibition of beta-glucosidase from Bacillus polymyxa (BGLA). The kinetic properties and structural analysis of BGLA in the presence of glucose-6-phosphate (G6P) were investigated. Kinetic studies demonstrated that enzyme was not inhibited by G6P. In contrast, the presence of G6P activated the enzyme, prevented beta glucosidase feedback inhibition by glucose accumulation and improved protein stability. G6P binding was investigated by fluorescence quenching experiments and the respective association constant indicated high affinity binding of G6P to BGLA. Data reported here are of great impact for future design strategies for second-generation bioethanol production.

Imobilização de lacase de Aspergillus sp. em quitosana e sua aplicação na bioconversão de fenóis em reatores de leito fixo

The immobilization of laccase on chitosan by cross-linking and application of the immobilized laccase in the bioconversion of phenolic compounds in batch and fixed bed reactors were studied. The process for immobilization of enzyme was optimized using a rotational central composite design. The optimized conditions to generate immobilized laccase with maximal activity were determined to be a glutaraldehyde concentration of 1.0% (v/v), a pH of 6.0, an immobilization time of 5.0 hours and an enzyme concentration of 5.2 g L-1. In packed bed reactors, the activity of the immobilized enzyme is maintained for a longer time in the bioconversion of 2,6-dimethoxyphenol than in the bioconversion of syringaldazine.

Otimização da esterificação de ácido hexanóico com n-butanol empregando lipase (Termomyces lanuginosus) imobilizada em gelatina

The application of Lipozyme (Termomyces lanuginosus) immobilized in gelatin gel in aliphatic ester synthesis was investigated taking the esterification of hexanoic acid with n-butanol as a model reaction. Conditions were optimized by factorial design and the highest conversion was obtained under the following conditions: molar ratio alcohol: acid of 2:1, reaction time of 48 h and biocatalyst weight of 7.0 g. Under these conditions the esterification yield was around 98 %. The operational stability of the immobilized lipase was assessed and results showed that after 12 batch runs, the enzyme showed no significant loss of activity.

Using natural biomass microorganisms for drinking water denitrification

Among the methods that are studied to eliminate nitrate from drinking water, biological denitrification is an attractive strategy. Although several studies report the use of denitrifying bacteria for nitrate removal, they usually involve the use of sewage sludge as biomass to obtain the microbiota. In the present study, denitrifying bacteria was isolated from bamboo, and variable parameters were controlled focusing on optimal bacterial performance followed by physicochemical analysis of water adequacy. In this way, bamboo was used as a source of denitrifying microorganisms, using either Immobilized Microorganisms (IM) or Suspended Microorganisms (SM) for nitrate removal. Denitrification parameters optimization was carried out by analysis of denitrification at different pH values, temperature, nitrate concentrations, carbon sources as well as different C/N ratios. In addition, operational stability and denitrification kinetics were evaluated. Microorganisms present in the biomass responsible for denitrification were identified as Proteus mirabilis. The denitrified water was submitted to physicochemical treatment such as coagulation and flocculation to adjust to the parameters of color and turbidity to drinking water standards. Denitrification using IM occurred with 73% efficiency in the absence of an external carbon source. The use of SM provided superior denitrification efficiency using ethanol (96.46%), glucose (98.58%) or glycerol (98.5%) as carbon source. The evaluation of the operational stability allowed 12 cycles of biomass reuse using the IM and 9 cycles using the SM. After physical-chemical treatment, only SM denitrified water remained within drinking water standards parameters of color and turbidity.

Improved enzymatic performance of graphene‐immobilized β‐glucosidase A in the presence of glucose‐6‐phosphate

Optimization of cellulose enzymatic hydrolysis is crucial for cost‐effective bioethanol production from lignocellulosic biomass. Enzyme immobilization in solid support allows enzyme recycling for reuse, lowering hydrolysis costs. Graphene is a nanomaterial isolated in 2004, which possesses exceptional properties for biomolecule immobilization. This study evaluates the potential for β‐glucosidase recycling by immobilization on graphene nanosheets. Data reported here demonstrated that graphene‐immobilized β‐glucosidase can be recycled for at least eight cycles. Immobilization did not change the optimal temperature of catalysis and improved enzymatic stability upon storage. The role of glucose‐6‐phosphate on immobilized enzyme was also investigated, demonstrating that glucose‐6‐phosphate acts as a mixed‐type activator and improves storage stability of immobilized enzyme. Complete cellulose hydrolysis using graphene‐immobilized β‐glucosidase in the presence of glucose‐6‐phosphate resulted in greatly improved hydrolysis rates, demonstrating the potential of this strategy for biomass hydrolysis.

Aplicação de Peroxidases no Tratamento de Efluentes

This revision exposes the use of oxidative enzymes in the treatment of specific contaminants of wastewater, like phenolic compounds, aromatic amines, textile dyes and polyaromatic hydrocarbons. Peroxidases belong to a group of oxidative enzymes distributed among several natural resources, which can degrade a wide variety of aromatic compounds. However, high costs of production difficult the widespread use of these enzymes for the wastewater remediation in industrial scale. Stand and pilot studies are showing that the enzymatic treatment of effluents can be a viable option for biodegradation of contaminants. In this article many studies using oxidative enzymes to carry out effluent treatment are covered.

TECNOLOGIAS EMPREGADAS NO TRATAMENTO DE EFLUENTES DE LATICÍNIOS DO VALE DO RIO BRAÇO DO NORTE - SC

Great amounts of effluents produced in dairy processing are associated to dairy production activities. Choosing an efficient system in the removal of contaminants may be a highly complex process due to the composition, variation in production rates and the effluent´s composition. Current paper provides the techniques employed to this end and, at the same time, delineate the profile of technologies applied by dairy factories in the region Vale do rio Braco do Norte, in the south of the state of Santa Catarina, Brazil, coupled to other aspects related to the dairies´ environmental management. Data, retrieved by a questionnaire and document evaluation, showed that the region´s dairy establishments predominantly apply anaerobic systems for the removal of biodegradable organic matter, with removal rates complying with legislation. However, other parameters, such as oils, fats, pH and sediment solids had higher rates than those stipulated by environmental organs. The firms´ environmental management is largely outsourced; in other words, they lack proper personnel technically capacitated for such work.

Optimization of Phenol Removal from Biorefinery Effluent Using Horseradish Peroxidase

AbstractBiorefinery is a facility comprising industrial processes for the production of fuel and chemicals from biomass. Because there is a growing number of biorefineries worldwide, the related en...