The potential of tailoring the conditions of steam explosion to produce xylo-oligosaccharides from sugarcane bagasse.

In this study, the potential of the steam explosion (SE) method to produce high levels XOS from sugarcane bagasse, a xylan-rich hemicellulosic feedstock, was assessed. The effect of different operating conditions on XOS production yield and selectivity were investigated using a mini-pilot scale SE unit. The results show that even under a non-optimized condition (190 °C, 5 min and 0.5% H2SO4 as catalyst), SE led to about 40% xylan recovery as XOS, which was comparable to the well-known, multi-step, enzymatic production of XOS from alkaline-extracted xylan, and other commonly employed chemical methods. In addition, the XOS-rich hydrolysate from SE constituted of greater diversity in the degree of polymerization, which has been shown to be desirable for prebiotic application.

Chemical input reduction in the arabinoxylan and lignocellulose alkaline extraction and xylooligosaccharides production.

Lignocellulosic material breakdown by hydrolysis is an important step to open new perspectives for bioenergy and special foods production like prebiotic xylooligosaccharides. Improvement of lignocellulose and arabinoxylan alkaline extraction from sugarcane bagasse and enzymatic hydrolysis were performed. Treatments 1 (10% KOH at 70°C), 3 (5% KOH at 121°C) and ZD method (24% KOH at 35°C) showed solid lignocellulose recovery of respectively 75.2%, 74.2% and 73%. A range of 24.8-27% extracted material with high arabinoxylan content (72.1-76.3%) was obtained with these treatments. Treatment 1 and 3 exhibited great KOH reduction in the method reaction, 54.1% and 76.2%, respectively. Likewise, in treatment 3 there was a decrease in ethanol consumption (40.9%) when compared to ZD method. The extracted arabinoxylan showed susceptibility to enzymatic hydrolysis with high solid loading (7%) since Trichoderma reesei xylanases were advantageous for xylose production (54.9%), while Aspergillus fumigatus xylanases achieved better XOS production (27.1%).

Immobilization of Papain on Chitin and Chitosan and Recycling of Soluble Enzyme for Deflocculation of Saccharomyces cerevisiae from Bioethanol Distilleries.

Yeast flocculation (Saccharomyces cerevisiae) is one of the most important problems in fuel ethanol production. Yeast flocculation causes operational difficulties and increase in the ethanol cost. Proteolytic enzymes can solve this problem since it does not depend on these changes. The recycling of soluble papain and the immobilization of this enzyme on chitin or chitosan were studied. Some cross-linking agents were evaluated in the action of proteolytic activity of papain. The glutaraldehyde (0.1-10% w·v(-1)), polyethyleneimine (0.5% v·v(-1)), and tripolyphosphate (1-10% w·v(-1)) inactivated the enzyme in this range, respectively. Glutaraldehyde inhibited all treatments of papain immobilization. The chitosan cross-linked with TPP in 5 h of reaction showed the yield of active immobilized enzyme of 15.7% and 6.07% in chitosan treated with 0.1% PEI. Although these immobilizations have been possible, these levels have not been enough to cause deflocculation of yeast cells. Free enzyme was efficient for yeast deflocculation in dosages of 3 to 4 g·L(-1). Recycling of soluble papain by centrifugation was effective for 14 cycles with yeast suspension in time perfectly compatible to industrial conditions. The reuse of proteases applied after yeast suspension by additional yeast centrifugation could be an alternative to cost reduction of these enzymes.

Screening of Xylanolytic Aspergillus fumigatus for Prebiotic Xylooligosaccharide Production Using Bagasse.

Sugarcane bagasse is an important lignocellulosic material studied for the production of xylooligosaccharides (XOS). Some XOS are considered soluble dietary fibre, with low caloric value and prebiotic effect, but they are expensive and not easily available. In a screening of 138 fungi, only nine were shortlisted, and just Aspergillus fumigatus M51 (35.6 U/mL) and A. fumigatus U2370 (28.5 U/mL) were selected as the most significant producers of xylanases. These fungi had low ß-xylosidase activity, which is desirable for the production of XOS. The xylanases from Trichoderma reesei CCT 2768, A. fumigatus M51 and A. fumigatus U2370 gave a significantly higher XOS yield, 11.9, 14.7 and 7.9% respectively, in a 3-hour reaction with hemicellulose from sugarcane bagasse. These enzymes are relatively thermostable at 40-50 °C and can be used in a wide range of pH values. Furthermore, these xylanases produced more prebiotic XOS (xylobiose and xylotriose) when compared with a commercial xylanase. The xylanases from A. fumigatus M51 reached a high level of XOS production (37.6%) in 48-72 h using hemicellulose extracted from sugarcane bagasse. This yield represents 68.8 kg of prebiotic XOS per metric tonne of cane bagasse. In addition, in a biorefinery, after hemicellulose extraction for XOS production, the residual cellulose could be used for the production of second-generation ethanol.

Chemical inhibition of the contaminant Lactobacillus fermentum from distilleries producing fuel bioethanol

The purpose of this study was to determine the Minimum Inhibitory Concentration (MIC) of pure or mixed chemicals for Saccharomyces cerevisiae and Lactobacillus fermentum in the samples isolated from distilleries with serious bacterial contamination problems. The biocides, which showed the best results were: 3,4,4' trichlorocarbanilide (TCC), tested at pH 4.0 (MIC = 3.12 mg/l), TCC with benzethonium chloride (CBe) at pH 6.0 (MIC = 3.12 mg/l) and TCC mixed with benzalkonium chloride (CBa) at pH 6.0 (MIC = 1.53 mg /l). If CBa was used in sugar cane milling in 1:1 ratio with TCC, a 8 times reduction of CBa was possible. This formulation also should be tested in fermentation steps since it was more difficult for the bacterium to develop resistance to biocide. There was no inhibition of S. cerevisiae and there were only antibiotics as an option to bacterial control of fuel ethanol fermentation by S. cerevisiae.

Purification and characterization of the alpha-glucosidase produced by thermophilic fungus Thermoascus aurantiacus CBMAI 756.

An alpha-glucosidase enzyme produced by the fungus Thermoascus aurantiacus CBMAI 756 was purified by ultra filtration, ammonium sulphate precipitation, and chromatography using Q Sepharose, Sephacryl S-200, and Superose 12 columns. The apparent molecular mass of the enzyme was 83 kDa as determined in gel electrophoresis. Maximum activity was observed at pH 4.5 at 70 degrees C. Enzyme showed stability stable in the pH range of 3.0-9.0 and lost 40% of its initial activity at the temperatures of 40, 50, and 60 degrees C. In the presence of ions Na(+), Ba(2+), Co(2+), Ni(2+), Mg(2+), Mn(2+), Al(3+), Zn(2+), Ca(2+) this enzyme maintained 90-105% of its maximum activity and was inhibited by Cr(3+), Ag(+), and Hg(2+). The enzyme showed a transglycosylation property, by the release of oligosaccharides after 3 h of incubation with maltose, and specificity for short maltooligosaccharides and alpha-PNPG. The K(m) measured for the alpha-glucosidase was 0.07 microM, with a V(max) of 318.0 micromol/min/mg.

Localization and partial characterization of thermostable glucoamylase produced by newly isolated Thermomyces lanuginosus TO3 in submerged fermentation

Thermophilic Thermomyces lanuginosus strain TO3 was isolated from compost pile samples and was used for its ability to produce considerable glucoamylase activity when growing in liquid medium at 45ºC with starch as the sole carbon source. Enzyme productivity was high in submerged fermentation (SmF) with maximum activity of 13 U/mL after 168 h of fermentation. Higher quantities of glucose were released when the substrate for enzyme was soluble starch than maltose or maltooligosaccharides were used. The distribution of glucoamylase between the extracellular and cell-associated fractions varied according to fermentation time. Glucoamylase produced from T. lanuginosus TO3 had optimum activity at 65 ºC and good thermostability in the absence of substrate, with a half-life of 6 h at 60 ºC. The enzyme was stable over a wide pH range (4.0-10.0).

O fungo termofílico Thermomyces lanuginosus TO3 foi isolado a partir de amostras de material de pilhas de compostagem, com base em sua capacidade de crescer em meio líquido contendo amido como única fonte de carbono, a 45 ºC, e produzir considerável quantidade de glucoamilase. A produção da enzima por fermentação submersa FSm foi alta, com um máximo de 13 U/mL em 168 h de fermentação. A atividade enzimática foi maior sobre amido do que sobre a maltose e maltooligosacarideos. As atividades de glucoamilase extra e intracelular variaram com o tempo de fermentação. A glucoamilase produzidas por T. lanuginosus TO3 apresentou elevada temperatura ótima de atividade (65 -70 ºC) com boa termoestabilidade em ausência de substrato, apresentando uma meia vida de 6 h a 60ºC, além de estabilidade em ampla faixa de pH. Os resultados apresentados indicam uma importante fonte alternativa de glucoamilase para uso no processamento industrial de amido.

A specific short dextrin-hydrolyzing extracellular glucosidase from the thermophilic fungus Thermoascus aurantiacus 179-5.

The thermophilic fungus Thermoascus aurantiacus 179-5 produced large quantities of a glucosidase which preferentially hydrolyzed maltose over starch. Enzyme production was high in submerged fermentation, with a maximal activity of 30 U/ml after 336 h of fermentation. In solid-state fermentation, the activity of the enzyme was 22 U/ml at 144 h in medium containing wheat bran and 5.8 U/ml at 48 h when cassava pulp was used as the culture medium. The enzyme was specific for maltose, very slowly hydrolyzed starch, dextrins (2-7G) and the synthetic substrate (alpha-PNPG), and did not hydrolyze sucrose. These properties suggest that the enzyme is a type II alpha-glucosidase. The optimum temperature of the enzyme was 70 degrees . In addition, the enzyme was highly thermostable (100% stability for 10 h at 60 degrees and a half-life of 15 min at 80 degrees), and stable within a wide pH range.