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.

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.