ABSTRACT
Abstract This study evaluated the effects of three chemical pretreatments of biomass sorghum (BS): dilute alkaline (PTA1 and PTA2), dilute acid (PTB1 and PTB2) and alkaline hydrogen peroxide (PTC1 and PTC2) in the enzymatic hydrolysis and ethanol production. Among the six investigated conditions, the pretreatment with 7.36% H2O2 (PTC2) was the most efficient in the lignin removal and preservation of the polysaccharide fraction. After the enzymatic hydrolysis, increases in the glucose and xylose concentrations were observed in the pretreated BS hydrolysates, mainly in PTB1 and PTC1. All the hydrolysates obtained low concentrations of inhibitors. In the alcoholic fermentations with Pichia stiptis, the greatest ethanol yield was obtained in PTB1 hydrolysate (3.84 g L-1), corresponding to 16.15% of yield. The highest ethanol yield in PTB1 hydrolysate can be justified by the maximum concentration of xylose obtained in this hydrolysate, demonstrating the potential of P. stiptis in the fermentation of pentose to ethanol. The results indicated that biomass sorghum is an alternative lignocellulose source with potential for the production of second generation ethanol, opening up prospects for additional studies.
Subject(s)
Biomass , Ethanol , Chemical Phenomena , Hydrogen Peroxide , Metals, AlkaliABSTRACT
This study reports the optimization of xylanase production under solid state fermentation (SSF) by a thermotolerant Aspergillus fumigatus strain (SCB4) isolated from sugarcane bagasse piles of Brazilian Cerrado. Different combinations of low-cost agricultural byproducts in SSF were evaluated: sugarcane bagasse and wheat bran (1:1), sugarcane bagasse and corn straw (1:1) and only sugarcane bagasse. The enzyme biosynthesis by SSF was carried out at different temperatures (40, 45, 50 and 55 oC). The maximum levels of xylanase activity were obtained after 24 h at 45 °C using a culture medium containing sugarcane bagasse and wheat bran (1:1). Under optimal conditions, the fungal culture produced 574 U g-1 of xylanase (units/g of dry substrate). The crude enzyme showed optimal activity at 60 °C and pH 4.5. It exhibited thermostability up to 55 °C, wide range of pH stability and tolerance to ethanol, xylose and glucose. The physicochemical properties shown by this enzyme are appropriate for its application in hydrolysis of lignocellulosic residues for ethanol production and other bioproducts.
Este estudo descreve a otimização da produção de xilanase por fermentação em estado sólido (FES) por uma linhagem termotolerante de Aspergillus fumigatus isolada de pilhas de bagaço de cana-de-açúcar do Cerrado Brasileiro (linhagem SCB4). Combinações de diferentes subprodutos agrícolas de baixo custo foram avaliadas como substratos na FES: bagaço de cana-de-açúcar e farelo de trigo (1:1), bagaço de cana-de-açúcar e palha de milho (1:1) e somente bagaço de cana-de-açúcar. A produção da enzima por FES foi realizada em diferentes temperaturas (40, 45, 50 e 55 oC). Níveis máximos de xilanase (574 U g-1 de substrato seco) foram obtidos após 24 h a 45 °C, utilizando bagaço de cana-de-açúcar e farelo de trigo (1:1) no meio de cultura. O extrato enzimático bruto apresentou atividades ótimas a 60 °C e pH 4,5. A enzima exibiu estabilidade térmica até 55 °C, ampla faixa de pH de estabilidade e tolerância ao etanol, xilose e glucose. Tais propriedades físico-químicas indicam que o extrato enzimático obtido é apropriado para aplicação na hidrólise de resíduos lignocelulósicos para a produção de etanol e outros bioprodutos.
Subject(s)
Aspergillus fumigatus , Zea mays , Saccharum , Industrial WasteABSTRACT
Nineteen fungi and seven yeast strains were isolated from sugarcane bagasse piles from an alcohol plant located at Brazilian Cerrado and identified up to species level on the basis of the gene sequencing of 5.8S-ITS and 26S ribosomal DNA regions. Four species were identified:
Subject(s)
Aspergillus fumigatus/enzymology , Aspergillus niger/enzymology , Cellulose/metabolism , /metabolism , Kluyveromyces/enzymology , Saccharum/microbiology , Xylosidases/metabolism , beta-Glucosidase/metabolism , Aspergillus fumigatus/isolation & purification , Aspergillus fumigatus/metabolism , Aspergillus niger/isolation & purification , Aspergillus niger/metabolism , Base Sequence , Biomass , Brazil , DNA, Fungal/genetics , DNA, Intergenic/genetics , Fermentation , Kluyveromyces/isolation & purification , Kluyveromyces/metabolism , Lignin/metabolism , Molecular Typing , Mycological Typing Techniques , RNA, Ribosomal/genetics , Sequence Analysis, DNAABSTRACT
The cattle tick Boophilus microplus causes great damage in livestock and is considered one of the most important tropical ectoparasites. The traditional method of control is based on the intensive use of pesticides, however the indiscriminate use of these compounds over the years has led to the selection of resistant ticks. Hydrolases, particularly esterases (EST), have been reported to be associated with acaricide resistance in B. microplus. We compared the esterase profile of susceptible and cypermethrin-resistant strains of adult B. microplus and a pyrethroid susceptible reference strain (the Mozzo strain) using polyacrylamide gel electrophoresis and specific staining. The electrophoretic profiles of protein extracts revealed the presence of four regions with esterase activity in the cypermethrin-resistant strain and three of these regions in the susceptible strains. The bands were numbered EST-1 to EST-4 in sequence (starting from the anode) according to their decrease in negative charge. The EST-1A and EST-1B enzymes were detected only in the resistant strain. The inhibition studies with eserine sulfate, copper sulfate, p- p-chloromercuribenzoate (pCMB), malathion and phenylmethylsulfonyl fluoride (PMSF) indicated that the EST-1A and EST-1B enzymes belong to the acetylcholinesterase class and are probably associated with resistance to acaricides in this Brazilian resistant strain of B. microplus.