Xylose reductase (XR) is an intracellular enzyme, which catalyzes xylose to xylitol conversion in the microbes. It has potential biotechnological applications in the manufacture of various commercially important specialty bioproducts including xylitol. This study aimed to prepare XR from adapted strain of Candida tropicalis and to characterize it. The XR was isolated from adapted C. tropicalis, cultivated on Meranti wood sawdust hemicellulosic hydrolysate (MWSHH)-based medium, via ultrasonication, and was characterized based on enzyme activity, stability, and kinetic parameters. It was specific to NADPH with an activity of 11.16 U/mL. The enzyme was stable at pH 5-7 and temperature of 25-40 °C for 24 h and retained above 95 % of its original activity after 4 months of storage at -80 °C. The K m of XR for xylose and NADPH were 81.78 mM and 7.29 μM while the V max for them were 178.57 and 12.5 μM/min, respectively. The high V max and low K m values of XR for xylose reflect a highly productive reaction among XR and xylose. MWSHH can be a promising xylose source for XR preparation from yeast.
Xylose-rich sawdust hydrolysate can be an economic substrate for the enzymatic production of xylitol, a specialty product. It is important to identify the process factors influencing xylitol production. This research aimed to screen the parameters significantly affecting bioxylitol synthesis from wood sawdust by xylose reductase (XR). Enzymatic bioxylitol production was conducted to estimate the effect of different variables reaction time (2-18 h), temperature (20-70 °C), pH (4.0-9.0), NADPH (1.17-5.32 g/L), and enzyme concentration (2-6 %) on the yield of xylitol. Fractional factorial design was followed to identify the key process factors. The screening design identified that time, temperature, and pH are the most significant factors influencing bioxylitol production among the variables with the values of 12 h, 35 °C, and 7.0, respectively. These conditions led to a xylitol yield of 71 % (w/w). This is the first report on the statistical screening of process variables influencing enzyme-based bioxylitol production from lignocellulosic biomass.
Aldose reductase is an important enzyme in the polyol pathway, where glucose is converted to fructose, and sorbitol is released. Aldose reductase activity increases in diabetes as the glucose levels increase, resulting in increased sorbitol production. Sorbitol, being less cell permeable tends to accumulate in tissues such as eye lenses, peripheral nerves and glomerulus that are not insulin sensitive. This excessive build-up of sorbitol is responsible for diabetes associated complications such as retinopathy and neuropathy. In continuation of our interest to design and discover potent inhibitors of aldo-keto reductases (AKRs; aldehyde reductase ALR1 or AKR1A, and aldose reductase ALR2 or AKR1B), herein we designed and investigated a series of new benzoxazinone-thiosemicarbazones (3a-r) as ALR2 and ALR1 inhibitors. Most compounds exhibited excellent inhibitory activities with IC50 values in lower micro-molar range. Compounds 3b and 3l were found to be most active ALR2 inhibitors with IC50 values of 0.52 ± 0.04 and 0.19 ± 0.03 μM, respectively, both compounds were more effective inhibitors as compared to the standard ALR2 inhibitor (sorbinil, with IC50 value of 3.14 ± 0.02 μM).