The boosting effect of recombinant hemicellulases on the enzymatic hydrolysis of steam-treated sugarcane bagasse.

To increase the efficiency of enzyme cocktails in deconstructing cellulose and hemicelluloses present in the plant cell wall, a combination of enzymes with complementary activities is required. Xylan is the main hemicellulose component of energy crops and for its complete hydrolysis a system consisting of several enzymes acting cooperatively, including endoxylanases (XYN), ß-xylosidases (XYL) and α-l-arabinofuranosidases (ABF) is necessary. The current work aimed at evaluating the effect of recombinant hemicellulolytic enzymes on the enzymatic hydrolysis of steam-exploded sugarcane bagasse (SEB). One recombinant endoxylanase (HXYN2) and one recombinant ß-xylosidase (HXYLA) from Humicola grisea var thermoidea, together with an α-l-arabinofuranosidase (AFB3) from Penicillium pupurogenum, all produced in Pichia pastoris, were used to formulate an efficient enzyme mixture for SEB hydrolysis using a 23 Central Composite Rotatable Design (CCRD). The most potent enzyme for SEB hydrolysis was ABF3. Subsequently, the optimal enzyme mixture was used in combination with commercial cellulases (Accellerase 1500), either simultaneously or in sequential experiments. The supplementation of Accellerase 1500 with hemicellulases enhanced the glucose yield from SEB hydrolysis by 14.6%, but this effect could be raised to 50% when hemicellulases were added prior to hydrolysis with commercial cellulases. These results were supported by scanning electron microscopy, which revealed the effect of enzymatic hydrolysis on SEB fibers. Our results show the potential of complementary enzyme activities to improve enzymatic hydrolysis of SEB, thus improving the efficiency of the hydrolytic process.

Improvement of bread making quality by supplementation with a recombinant xylanase produced by Pichia pastoris.

Xylanases (EC 3.2.1.8) are hydrolytic enzymes, which randomly cleave the ß-1,4-linked xylose residues from xylan. The synthetic gene xynBS27 from Streptomyces sp. S27 was successfully cloned and expressed in Pichia pastoris. The full-length gene consists of 729 bp and encodes 243 amino acids including 51 residues of a putative signal peptide. This enzyme was purified in two steps and was shown to have a molecular weight of 20 kDa. The purified r-XynBS27 was active against beechwood xylan and oat spelt xylan as expected for GH 11 family. The optimum pH and temperature values for the enzyme were 6.0 and 75 °C, respectively. The Km and Vmax were 12.38 mg/mL and 13.68 µmol min/mg, respectively. The r-XynBS27 showed high xylose tolerance and was inhibited by some metal ions and by SDS. r-XynBS27 was employed as an additive in the bread making process. A decrease in firmness, stiffness and consistency, and improvements in specific volume and reducing sugar content were recorded.

Expression of EGF receptors in canine prostate with proliferative inflammatory atrophy and carcinoma / Expressão de receptores EGF na próstata canina com atrofia inflamatória proliferativa e carcinoma

ABSTRACT: Gene expression of ErbB1 and ErbB2, and immunostaining of EGFR (Her1) and Her2 (c-erbB-2) were evaluated in this study to ascertain whether these receptors are involved in the evolution of canine premalignant and malignant prostatic lesions, as proliferative inflammatory atrophy (PIA) and prostatic carcinoma (PC). With regards to the intensity of EGFR immunostaining, there was no difference between normal prostatic tissue and tissues with PIA or PC. In relation to Her2 immunostaining, there were differences between normal prostatic tissue and those with PIA and PC, as also differences between prostates with PIA and PC. There was no correlation between EGFR and Her2 immunostaining. ErbB1 gene product was detected in two normal tissue samples, in one with PIA, and in all samples with PC. ErbB2 mRNA was recorded in two canine samples with PIA, in all with PC, but was not detected in normal prostatic tissue. It was concluded that EGFR and Her2 play roles in canine PIA and PC, suggesting that those receptors may be involved in canine prostatic carcinogenesis.

RESUMO: A expressão gênica de ErbB1 e ErbB2 e a imunomarcação de EGFR (Her1) e Her2 (c-erbB-2) foram avaliadas para verificar o envolvimento desses receptores em lesões pré-malignas e malignas da próstata canina, como a atrofia proliferativa inflamatória (PIA) e o carcinoma prostático (PC). Em relação à intensidade de imunomarcação para EGFR, não houve diferença entre o tecido prostático normal e com PIA e PC. Em relação a Her2, observou-se diferença de imunomarcação entre o tecido prostático normal e aqueles com PIA e PC e entre os com PIA e PC. Não houve correlação entre EGFR e Her2. O gene ErbB1 foi detectado em duas amostras normais, uma de PIA e em todas as amostras de PC. O gene ErbB2 foi detectado em duas amostras de PIA e em todas as amostras de PC, não sendo detectado no tecido prostático normal. Conclui-se que EGFR e Her2 atuam nas lesões de PIA e PC, sugerindo o envolvimento destes na carcinogênese da próstata canina.

Characterization of a recombinant xylose tolerant ß-xylosidase from Humicola grisea var. thermoidea and its use in sugarcane bagasse hydrolysis.

One full-length ß-xylosidase gene (hxylA) was identified from the Humicola grisea var. thermoidea genome and the cDNA was successfully expressed by Pichia pastoris SMD1168. An optimization of enzyme production was carried out, and methanol was found to be the most important parameter. The purified enzyme was characterized and showed the optimal conditions for the highest activity at pH 7.0 and 50°C, being thermostable by maintaining 41% of its activity after 12h incubated at 50°C. HXYLA is a bifunctional enzyme; it showed both ß-xylosidase and α-arabinfuranosidase activities. The Km and Vmax values were 1.3mM and 39.1U/mg, respectively, against 4-nitrophenyl ß-xylopyranoside. HXYLA showed a relatively strong tolerance to xylose with high Ki value of 603mM, with the xylose being a non-competitive inhibitor. HXYLA was successfully used simultaneously and sequentially with an endo-xylanase for analysis of synergism in the degradation of commercial xylans. Furthermore, commercial cellulases supplementation with HXYLA during sugarcane bagasse hydrolysis increased hydrolysis in 29%. HXYLA is distinguished from other ß-xylosidases by the attractive characteristics for industrial applications such as thermostability, high tolerance xylose and saccharification of biomass by convert xylan into fementable monosaccharides and improve cellulose hydrolysis.