Abstract
Xylose reductase (XR) is a key enzyme in order to obtain xylitol from xylose. It has vast applications in biotechnology including xylitol production. The present study aimed to estimate and characterize XR from Candida tropicalis strain LY15. C. tropicalis strain LY15 showed xylose utilization ability and xylose reductase activity after 48 h of incubation at pH 6.5, incubation temperature 28°C and rotation speed 140 rpm. It was specific to nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) with an activity of 32.13 IU/ml. Response surface methodology (RSM) was taken into account in order to determine the effect of four main factors, that is, inoculum (1%), hemicellulose waste substrates (HWs) (2%), incubation period (60 h), and RPM (140) on enzyme production. The maximum XR enzyme activity on corn cob substrates (62.80 IU/ml) was found. The xylitol yield (12.08 g/L) attained corn cob media after 60 h of fermentation. Three dimensional response and interaction plot of the quadratic model showed interdependent interaction between the effective variables. Analysis of variance (ANOVA) predicts R2 value close to 1 which makes the result highly significant (p≤0.0001). These values were higher when compared with the traditional fermentation processes. Key words: Candida tropicalis, corn cob, xylitol, response surface methodology (RSM), xylose reductase.
Highlights
Yeasts have played an important role in industrial development for thousands of years
Effect of different parameters in fermentation condition for xylitol production based on Xylose reductase (XR) assay
Xylose assimilation is catalyzed by xylitol dehydrogenase and XR
Summary
Yeasts have played an important role in industrial development for thousands of years. Yeast is a group of fungi predominantly containing unicellular form. Many types of yeasts are used in food, baking industries and fermentation for xylitol production. The enzyme catalyzed the xylose, which can be further converted into xylulose. Xylitol has been considered to trigger the expression of xylanolytic enzymes (Margolles-Clark et al, 1997; Usvalampi, 2013). Xylitol is a naturally occurring sugar alcohol. The calories of xylitol are less when compared with sucrose based upon on mass and has similar sweetness, which permit its applications in food industries with anticarcinogenic activities, or in medicines (Saha et al, 1997). Xylans are converted into xylitol, a potential substitute of sugar for diabetic patients (Barthikannan et al, 2016)
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