The yeast <Emphasis Type="Italic">Scheffersomyces amazonensis</Emphasis> is an efficient xylitol producer

This study assessed the efficiency of Scheffersomyces amazonensis UFMG-CM-Y493^T, cultured in xylose-supplemented medium (YPX) and rice hull hydrolysate (RHH), to convert xylose to xylitol under moderate and severe oxygen limitation. The highest xylitol yields of 0.75 and 1.04 g g^?1 in YPX and RHH, respectively, were obtained under severe oxygen limitation. However, volumetric productivity in RHH was ninefold decrease than that in YPX medium. The xylose reductase (XR) and xylitol dehydrogenase (XDH) activities in the YPX cultures were strictly dependent on NADPH and NAD⁺ respectively, and were approximately 10% higher under severe oxygen limitation than under moderate oxygen limitation. This higher xylitol production observed under severe oxygen limitation can be attributed to the higher XR activity and shortage of the NAD⁺ needed by XDH. These results suggest that Sc. amazonensis UFMG-CM-Y493^T is one of the greatest xylitol producers described to date and reveal its potential use in the biotechnological production of xylitol.     

Identification and characterisation of xylanolytic yeasts isolated from decaying wood and sugarcane bagasse in Brazil

In this study, yeasts associated with lignocellulosic materials in Brazil, including decaying wood and sugarcane bagasse, were isolated, and their ability to produce xylanolytic enzymes was investigated. A total of 358 yeast isolates were obtained, with 198 strains isolated from decaying wood and 160 strains isolated from decaying sugarcane bagasse samples. Seventy-five isolates possessed xylanase activity in solid medium and were identified as belonging to nine species: Candida intermedia, C. tropicalis, Meyerozyma guilliermondii, Scheffersomyces shehatae, Sugiyamaella smithiae, Cryptococcus diffluens, Cr. heveanensis, Cr. laurentii and Trichosporon mycotoxinivorans. Twenty-one isolates were further screened for total xylanase activity in liquid medium with xylan, and five xylanolytic yeasts were selected for further characterization, which included quantitative analysis of growth in xylan and xylose and xylanase and β-d-xylosidase activities. The yeasts showing the highest growth rate and cell density in xylan, Cr. laurentii UFMG-HB-48, Su. smithiae UFMG-HM-80.1 and Sc. shehatae UFMG-HM-9.1a, were, simultaneously, those exhibiting higher xylanase activity. Xylan induced the highest level of (extracellular) xylanase activity in Cr. laurentii UFMG-HB-48 and the highest level of (intracellular, extracellular and membrane-associated) β-d-xylosidase activity in Su. smithiae UFMG-HM-80.1. Also, significant β-d-xylosidase levels were detected in xylan-induced cultures of Cr. laurentii UFMG-HB-48 and Sc. shehatae UFMG-HM-9.1a, mainly in extracellular and intracellular spaces, respectively. Under xylose induction, Cr. laurentii UFMG-HB-48 showed the highest intracellular β-d-xylosidase activity among all the yeast tested. C. tropicalis UFMG-HB 93a showed its higher (intracellular) β-d-xylosidase activity under xylose induction and higher at 30 °C than at 50 °C. This study revealed different xylanolytic abilities and strategies in yeasts to metabolise xylan and/or its hydrolysis products (xylo-oligosaccharides and xylose). Xylanolytic yeasts are able to secrete xylanolytic enzymes mainly when induced by xylan and present different strategies (intra- and/or extracellular hydrolysis) for the metabolism of xylo-oligosaccharides. Some of the unique xylanolytic traits identified here should be further explored for their applicability in specific biotechnological processes.     

Novel O-palmitolylated beta-E1 subunit of pyruvate dehydrogenase is phosphorylated during ischemia/reperfusion injury

Background  

During and following myocardial ischemia, glucose oxidation rates are low and fatty acids dominate as a source of oxidative metabolism. This metabolic phenotype is associated with contractile dysfunction during reperfusion. To determine the mechanism of this reliance on fatty acid oxidation as a source of ATP generation, a functional proteomics approach was utilized.     

Effect of the Rho kinase inhibitor Y-27632 on the proteome of hearts with ischemia-reperfusion injury

Growing attention has been given to the role of the Rho kinase pathway in the development of heart disease and ischemia/reperfusion (I/R) injury. Y‐27632 is a Rho kinase inhibitor demonstrated to protect against I/R injury, but the exact mechanism by which it does so remains to be elucidated. The goal of this project was to determine new targets by which Y‐27632 can protect the heart against I/R injury. Isolated rat hearts were perfused under aerobic conditions or subjected to I/R in the presence or absence of Y‐27632. Administration of Y‐27632 (1 μM) before ischemia and during the first 10 min of reperfusion resulted in complete recovery of cardiac function. 2‐D electrophoresis followed by MS identified four proteins whose levels were affected by Y‐27632 treatment. Lactate dehydrogenase and glyceraldehyde‐3‐phosphate dehydrogenase were significantly increased in the Y‐27632 treated group, while creatine kinase was normalized to control levels. In addition, we found increased level of two different molecular fragments of ATP synthase, which were normalized by Y‐27632. This increase suggests that during ischemia ATP synthase is subjected to degradation. The changes in metabolic enzymes' levels and their regulation by Y‐27632 suggest that the cardioprotective effect of Y‐27632 involves increased energy production.