Xylose Reductase Production Research Articles

Effects of agitation rate and dissolved oxygen on xylose reductase activity during xylitol production at bioreactor scale

The study of xylose reductase (XR) - one of the key enzymes in the production of xylitol - is important in the fermentation process to have maximum efficiency in the bioconversion of xylose to xylitol in lignocellulosic hydrolysate. The aim was to evaluate the effect of agitation rate and dissolved oxygen at 7 L bioreactor scale on the production of xylose reductase (XR) from Candida tropicalis during the bioconversion of xylose into xylitol in the non-detoxified oil palm empty fruit bunch (OPEFB) hydrolysate. The highest xylose consumption (95.5%) and the maximum xylitol production (5.46 g.L-1) were presented under 30% dissolved oxygen and 50 rpm. The maximum XR activity (0.646 U mg-1 protein) was obtained after 144 h of fermentation and at the same conditions of dissolved oxygen and agitation rate mentioned above. The oxygen availability influences the XR activity of C. tropicalis and the xylitol production, observing a xylitol yield factor (YP/S) of 0.27 g.g-1 and volumetric productivity (QP) of 0.33 g.L-1 h-1. At lower dissolved oxygen regardless of the agitation conditions evaluated, an increase in xylitol production was evidenced.

Optimization of Xylose Reductase production from Citrobacter sp.

Xylitol is a poly-hydroxy straight-chain five-carbon alcohol that can replace sugar in daily uses without any side effects. Lowered risk of dental carries and bone demineralization further support its involvement in a healthy lifestyle. In addition, its role in the synthesis of various commercial products like glycol, ethanol, and resins etc. increases its market value and makes it one of the most valuable bio-products. Microbial fermentation is a cost-effective and eco-friendly method for xylitol production from agricultural residues as available xylose is reduced to xylitol by Xylose reductase (XR) using an equivalent amount of NADPH as a mediator for electron transfer. Previous literature emphasized the use of fungi and yeast for xylitol production rather than bacteria. In contrast to available reports, the potential of the bacterial isolate was evaluated for xylitol production. The effect of process parameters was observed on xylitol yield in terms of XR activity. Out of sixty-eight bacterial isolates obtained, XYLBV-05 was selected for XR production after screening and was identified as Citrobacter sp. based on morphological, microscopic, and biochemical characteristics. Parametric analysis increased the XR production by 4.12 folds (36.61 U/ml). Preliminary results also proved its efficiency in conversion of biomass hydrolysate to xylitol at lab scale but further efforts are needed for xylitol production using agro-industrial lignocellulosic biomass at a large scale which will not only aid in the generation of revenue as a result of value-added products but will also help in environment conservation.

Scale-up process for xylose reductase production using rice straw hydrolysate

Xylose reductase (XR), an industrially important enzyme, catalyzes the hydrogenation of xylose into xylitol. Xylitol, a polyol sugar, has tremendous applications in different industries due to its significant properties. XR is mainly produced from yeasts and molds, and limited studies have been reported on bacteria. The present study explores the potential of newly isolated bacteria, i.e., Pseudomonas putida BSX-46 for XR synthesis through process scale-up by tailoring its nutritional and cultural requirements. A simple media containing only four ingredients was designed for the production of XR in a short incubation time of 24 h. A process for pretreatment of rice straw was developed to achieve hydrolysate with a good amount of xylose (140 g/kg of rice straw). The enhanced XR production of 213.14±0.47 IU/mg of cells was achieved at bioreactor level using waste rice straw hydrolysate as compared to 94.26±0.62 IU/mg of cells at flask level. The developed bioprocess using efficient bacterial source and economical raw material would provide a low-cost substitute for XR production from xylose-based agro-waste materials at the industrial level.

PRODUCTION OF XYLOSE REDUCTASE AND XYLITOL BY Candida guilliermondii USING WHEAT STRAW HYDROLYSATES

The objective of this study is to evaluate the production of Xylose reductase (XR) and Xylitol by Candida guilliermondii using wheat straw hydrolysates (WSH) supplemented with 2.0 g/l of (NH4)2SO4 and 0.1 g/l of CaCl2.2H2O as fermentation media . Wheat straw hydrolysis run at 121°C for 15 min. by diluted sulfuric acid . The fermentation process was conducted on a shaker bath (150 rpm) at 30C for 20 h in three separate flasks using different concentration of Xylose being , 30% Xylose , WSH(27.13 g/l Xylose)and WSH plus 30 g/l Xylose. The best concentration( WSH plus 30 g/l Xylose ) was chosen to run the fermentation process for XR production at different incubation temperature ( 20, 25, 30, 35, 40, 45 C, different pH values (5, 5.5, 6, 6.5 and 7) and different fermentation period (5 , 10 , 15,20 ,25 ,30 h ). The results indicated that the optimum condition for XR production was using 30%Xylose plus WSH at pH 6 over 20h incubation at 30 C. The crude extract of Xylose reductase was used to reduce Xylose into Xylitol with simultaneous oxidation of NADPH. The crude extract of XR was able to convert about 90 % 0f the Xylose to Xylitol through 24 h. incubation at 30°C.According to these findings WSH can be used as a promising source for Xylose to produce Xylose reductase enzyme by Candida guilliermondii and the crude extract could be used successfully in conversion of Xylose to Xylitol.

Production of xylose reductase from adapted Candida tropicalis grown in sawdust hydrolysate

Abstract Xylose, recovered from Meranti wood sawdust (MWS), can be used as a promising and alternative carbon source for yeast growth as well as for the production of xylose reductase (XR). This enzyme has potential applications in the bioproduction of various high value products, especially xylitol. The aim of this study was to isolate XR from adapted yeast Candida tropicalis and to characterize it. The XR enzyme was prepared from C. tropicalis strain, grown in MWS hydrolysate-based medium, by ultrasonic homogenization. The isolated XR was characterized based on enzyme activity, stability, and kinetic constants. The activity of NADPH-dependent crude XR measured was 11.16 U/mL. It was stable at pH 5.0–7.0 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 apparent K m values of XR for xylose and NADPH were 81.78 mM and 7.29 μM while the V max for xylose and NADPH were 178.57 and 12.5 μM/min, respectively. The low K m,app and high V max,app values of XR for xylose as a substrate indicates a strong binding affinity for xylose and good productivity of the reaction.

Effect of Dissolved Oxygen and Inoculum Concentration on Xylose Reductase Production from <i>Candida guilliermondii</i> Using Sugarcane Bagasse Hemicellulosic Hydrolysate

This work evaluated the effect of dissolved oxygen and the initial inoculum concentration on xylose reductase (XR) production by Candida guilliermondii from sugarcane bagasse hemicellulosic hydrolysate. Both the parameters were studied under an experimental design 22 with triplicate at central point. The statistical analysis of the results indicated a significant negative effect on XR production from the variable inoculum. The variable dissolved oxygen also showed a negative effect on XR production. We found the maximum enzyme activity (2.5 U?mg?1) when both the factors were applied at their lowest levels. The yeast showed to be potentially capable for xylose reductase production when sugarcane bagasse hemicellulosic hydrolysate was used as carbon source. Also, the results presented important information for further optimization of xylose reductase attainment.

Increase in xylitol production by Candida tropicalis upon addition of salt

We examined the effect of salt on xylitol production by a 559-9 strain of Candida tropicalis. The addition of several different salts, including NaCl, KCl, and MgCl 2, increased xylitol production. Upon the addition of 4% NaCl, the maximum yield of xylitol from 5% D-xylose increased by about 1.3-fold. This effect of NaCl was reduced with increasing D-xylose concentrations in the medium. On the other hand, xylitol production is known to be suppressed in the presence of D-glucose. The addition of salts also increased the xylitol production even in the presence of 2% D-glucose. For example, the maximum yield of xylitol increased by about 1.6-fold upon addition of NaCl. These findings suggest that the addition of salt may be an effective means of increasing xylitol production when the hydrolysates of cellulosic materials, which contain low concentrations of D-xylose and D-glucose, are used as a substrate. Production of NADPH-dependent xylose reductase in cells grown on media containing 5% D-xylose increased upon addition of 4% NaCl. The increase in xylitol production by NaCl may be due in part to the increase in xylose reductase production.

Xylose reductase production by candida guilliermondii

Xylose reductase production by candida guilliermondii