Growth and proximate composition of Pleurotus ostreatuscultivated on green bocaiuva pulp substrates with different nitrogen sources

The aim of this work was to evaluate the growth and the proximate compositionof the mycelium-based bocaiuva pulp with the edible mushroom Pleurotusostreatuson green bocaiuva flour added with different sources of nitrogen (urea, ammonium nitrate and sulfate ammonia). Growth was monitored by kinectics. At the end, the proximate composition of the best three treatments (dehydrated green bocaiuva pulp and water, T1; dehydrated green bocaiuva pulp and ammonium nitrate, T3; and green bocaiuva pulp/wheat bran and ammonium nitrate, T7) was determined. Ammonium nitrate was the nitrogen source that showed the greatest growth in both substrates (T3:8.33 cm and T7:7.67 cm) in relation to the other treatments (4.67 to 7.17 cm), with emphasis on the green bocaiuva pulp. The substrate with green bocaiuva pulp and water was the one that showed the highest growth (7.50 cm), which was close to the treatment with mixed substrate and ammonium nitrate (7.67 cm). The treatment with the green bocaiuva pulp and ammonium nitrate (T3) was highlighted due to its significant increase in proteins (9.42 g 100 g-1) and fibers (5.21 g 100 g-1), and decrease in carbohydrates (9.52 g 100 g-1), in comparison to the other treatments T7 (8.94, 2.16, and 5.99 g 100 g-1, respectively) and T1 (2.78, 4.33, and 2.28 g 100 g-1, respectively). The product obtained from the growth of P. ostreatusin green bocaiuva pulp presents promising perspectives to be utilized as raw material for the development of new food products with added nutritional value.

Screening of an adapted culture medium composed by different carbon sources for heterotrophic cultivation of Chlorella vulgaris using a microplate assay / Triagem de um meio de cultura adaptado composto por diferentes fontes de carbono para o cultivo heterotrófico de Chlorella vulgaris usando um ensaio de microplacas

The ability of microalgae to grow heterotrophically lies in the ability to oxidize organic compounds present in the external environment. The aim of this work was to evaluate the growth of Chlorella vulgaris under heterotrophic culture conditions using Basal Bold and NPK media supplemented with different sole carbon sources (glucose, fructose, sucrose, glycerol or acetate). The kinetic parameters obtained were maximum specific growth rate (μmax), doubling time (DT), maximal absorbance, which was also converted to cell concentration values using a linear relation, and cell productivity (PX). Among all the treatments analyzed, the highest maximum specific growth rate found was 0.030 hour-1 (0.72 day-1) in the treatment using Basal Bold medium supplemented with glucose. The highest cellular concentration and cell productivity were also found for this same treatment (4.03 x 106 cell mL-1 and 64.0 x 106 cell L-1 day-1, respectively). It was concluded that that the Basal Bold medium was more efficient for Chlorella vulgaris growth, since it induced higher values of μmax and cellular concentration. Results obtained were very reproducible using microplate assay.

A capacidade das microalgas de crescer heterotroficamente reside na habilidade de oxidar compostos orgânicos presentes no ambiente externo. O objetivo deste trabalho foi avaliar o crescimento de Chlorella vulgaris em condições heterotróficas de cultura, usando meios Basal Bold e NPK, suplementados com diferentes fontes de carbono (glicose, frutose, sacarose, glicerol ou acetato). Os parâmetros cinéticos obtidos foram a velocidade específica máxima de crescimento (μmax), tempo de duplicação (TD), absorbância máxima, sendo que esta última também foi convertida em valores de concentração celular, usando uma relação linear e produtividade celular (PX). Entre todos os tratamentos analisados, a maior velocidade específica máxima de crescimento encontrada foi de 0,030 h-1 (0,72 dia-1) no tratamento usando o meio Basal Bold suplementado com glicose. A maior concentração celular e a maior produtividade celular também foram encontradas para esse mesmo tratamento (4,03 x 106 cel mL-1 e 64,0 x 106 cel L-1 dia-1, respectivamente). Concluiu-se que o meio Basal Bold foi mais eficiente para o crescimento de Chlorella vulgaris, pois induziu valores mais elevados de μmax e de concentração celular. Os resultados obtidos foram muito reproduzíveis, utilizando o ensaio de microplacas.

Production of xylanase by a new strain of Thermoascus aurantiacus: obtainment of enzymatic extract with reduced cellulolytic activity for application in pulp and paper industries / Produção de xilanase por nova linhagem de Thermoascus aurantiacus: obtenção de extrato enzimático com reduzida atividade celulolítica para aplicação em indústria de papel e celulose

Xylanases are useful in several industrial segments, including pulp and paper bleaching, animal feed, and bread-making processes. However, the industrial use of these enzymes is closely related to its production cost and its catalytic properties. The process of solid state fermentation enables the use of agro-industrial residues as substrates for microbial cultivation and enzymes production, reducing costs. In the present study, different cultivation parameters were evaluated for the xylanase production by the thermophilic fungus Thermoascus aurantiacus, by solid state fermentation, using agro-industrial residues as substrates. High production of xylanase (1701.9 U g-1 of dry substrate) was obtained using wheat bran containing 65% of initial moisture, at 120 h of cultivation, and 45°C. The xylanase showed optimal activity at pH 5.0 and 75°C; its stability was maintained at pH 3.0­11.0. The enzyme retained its catalytic potential after 1 h, at 75°C. The enzymatic extract produced under optimized conditions showed reduced activities of endoglucanase and FPase. Our results, including the xylanase production by T. aurantiacus in low-cost cultivation medium, high structural stability of the enzyme, and reduced cellulolytic activity, encourage the application of this enzymatic extract in pulp and paper bleaching processes.

As xilanases apresentam aplicabilidade em diferentes segmentos industriais, como: branqueamento de papel e celulose, ração animal e panificação. No entanto, a utilização industrial dessas enzimas está intimamente relacionada com seu custo de produção e suas propriedades catalíticas. O processo de fermentação em estado sólido possibilita o uso de resíduos agroindustriais como substratos, para o cultivo microbiano e produção de enzimas, reduzindo o custo da produção enzimática. No presente trabalho, diferentes parâmetros de cultivo foram avaliados para produção de xilanase por cultivo em estado sólido do fungo termófilo Thermoascus aurantiacus, utilizando resíduos agroindustriais como substratos. A maior produção de xilanase, 1701,9 U g-1 de substrato seco, foi obtida no cultivo em farelo de trigo, contendo 65% de umidade inicial, em 120 horas de cultivo a 45°C. A xilanase produzida apresentou atividade ótima em pH 5,0 a 75°C, mantendo sua estabilidade em pH 3,0 a 11,0. A enzima manteve seu potencial catalítico após 1 h a 75°C. O extrato enzimático produzido nas condições otimizadas apresentou reduzida atividade de endoglucanase e FPase. Os resultados obtidos no presente trabalho (produção de xilanase pelo fungo em meios de cultivo de baixo custo, elevada estabilidade estrutural da enzima e reduzida atividade celulolítica) estimulam a aplicação desse complexo enzimático em processos de branqueamento de papel e celulose.

Production of beta-glucosidase on solid-state fermentation by Lichtheimia ramosa in agroindustrial residues: characterization and catalytic properties of the enzymatic extract

Background β-Glucosidases catalyze the hydrolysis of cellobiose and cellodextrins, releasing glucose as the main product. This enzyme is used in the food, pharmaceutical, and biofuel industries. The aim of this work is to improve the β-glucosidase production by the fungus Lichtheimia ramosa by solid-state fermentation (SSF) using various agroindustrial residues and to evaluate the catalytic properties of this enzyme. Results A high production of β-glucosidase, about 274 U/g of dry substrate (or 27.4 U/mL), was obtained by cultivating the fungus on wheat bran with 65% of initial substrate moisture, at 96 h of incubation at 35°C. The enzymatic extract also exhibited carboxymethylcellulase (CMCase), xylanase, and β-xylosidase activities. The optimal activity of β-glucosidase was observed at pH 5.5 and 65°C and was stable over a pH range of 3.5-10.5. The enzyme maintained its activity (about 98% residual activity) after 1 h at 55°C. The enzyme was subject to reversible competitive inhibition with glucose and showed high catalytic activity in solutions containing up to 10% of ethanol. Conclusions β-Glucosidase characteristics associated with its ability to hydrolyze cellobiose, underscore the utility of this enzyme in diverse industrial processes.

Production of enzymes from Lichtheimia ramosa using Brazilian savannah fruit wastes as substrate on solid state bioprocessess

Background: Enzyme production by solid state bioprocess (SSB) using residues as substrate for microorganisms is an alternative for costs reduction and to avoid their disposal into environment. The aim of this work was to evaluate the physiology of the fungus Lichtheimia ramosa in terms of microbial growth and production of amylases, β-glucosidases, carboxymethylcellulase (CMCase), and xylanases, via SSB, utilizing wastes of the Brazilian savannah fruits bocaiuva (Acrocomia aculeata), guavira (Campomanesia pubescens) and pequi (Caryocar brasiliense) as substrate at different temperatures (25, 30, and 35ºC) during 168 hrs. Results: Samples were taken every 24 hrs, which resulted in 8-points kinetic experiments to determine microbiological and enzymatic contents. The best substrate for β-glucosidase activity was pequi waste after 48 hrs at 30ºC (0.061 U/mL). For amylase activity, bocaiuva presented itself as the best substrate after 96 hrs at 30ºC (0.925 U/mL). CMCase activity was higher in guavira waste after 96 hrs at 35ºC (0.787 U/mL). However, the activity was more expressive for xylanase in substrate composed of bocaiuva residue after 144 hrs at 35ºC (1.802 U/mL). Conclusions: It was concluded that best growth condition for L. ramosa is at 35ºC for all substrates and that xylanase is the enzyme with more potential in SSB, considering the studied Brazilian savannah fruit wastes.