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

2022 ◽  
Author(s):  
Katherine MANJARRES-PINZÓN ◽  
Dary MENDOZA-MEZA ◽  
Mario ARIAS-ZABALA ◽  
Guillermo CORREA-LONDOÑO ◽  
Eduardo RODRIGUEZ-SANDOVAL
Keyword(s):  
Dissolved Oxygen ◽  
Reductase Activity ◽  
Xylose Reductase ◽  
Agitation Rate ◽  
Xylitol Production

Simultaneous optimization of activity and stability of xylose reductase from D. nepalensis NCYC 3413 using statistical experimental design

2020 ◽  
Vol 27 ◽  
Author(s):  
Shwethashree Malla ◽  
Sathyanarayana N. Gummadi
Keyword(s):  
Half Life ◽  
Specific Activity ◽  
Enzyme Stability ◽  
Reductase Activity ◽  
Xylose Reductase ◽  
Life Time ◽  
Economic Feasibility ◽  
Simultaneous Optimization ◽  
Physical Parameters ◽  
Statistical Experimental Design

Background: Physical parameters like pH and temperature play a major role in the design of an industrial enzymatic process. Enzyme stability and activity are greatly influenced by these parameters; hence optimization and control of these parameters becomes a key point in determining the economic feasibility of the process. Objective: This study was taken up with the objective to optimize physical parameters for maximum stability and activity of xylose reductase from D. nepalensis NCYC 3413 through separate and simultaneous optimization studies and comparison thereof. Method: Effects of pH and temperature on the activity and stability of xylose reductase from Debaryomyces nepalensis NCYC 3413 were investigated by enzyme assays and independent variables were optimised using surface response methodology. Enzyme activity and stability were optimised separately and concurrently to decipher the appropriate conditions. Results: Optimized conditions of pH and temperature for xylose reductase activity were determined to be 7.1 and 27 ℃ respectively, with predicted responses of specific activity (72.3 U/mg) and half-life time (566 min). The experimental values (specific activity 50.2 U/mg, half-life time 818 min) were on par with predicted values indicating the significance of the model. Conclusion: Simultaneous optimization of xylose reductase activity and stability using statistical methods is effective as compared to optimisation of the parameters separately.

scholarly journals Spectroscopic analysis of myoglobin and cytochrome c dynamics in isolated cardiomyocytes during hypoxia and reoxygenation

2015 ◽  
Vol 12 (105) ◽  
pp. 20141339 ◽  
Author(s):  
A. Almohammedi ◽  
S. M. Kapetanaki ◽  
B. R. Wood ◽  
E. L. Raven ◽  
N. M. Storey ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Cellular Response ◽  
Ex Vivo ◽  
Reductase Activity ◽  
Sodium Dithionite ◽  
Raman Microspectroscopy ◽  
Chemical Agent ◽  
Rat Cardiomyocytes ◽  
Hypoxic Conditions ◽  
In Cells

Raman microspectroscopy was applied to monitor the intracellular redox state of myoglobin and cytochrome c from isolated adult rat cardiomyocytes during hypoxia and reoxygenation. The nitrite reductase activity of myoglobin leads to the production of nitric oxide in cells under hypoxic conditions, which is linked to the inhibition of mitochondrial respiration. In this work, the subsequent reoxygenation of cells after hypoxia is shown to lead to increased levels of oxygen-bound myoglobin relative to the initial levels observed under normoxic conditions. Increased levels of reduced cytochrome c in ex vivo cells are also observed during hypoxia and reoxygenation by Raman microspectroscopy. The cellular response to reoxygenation differed dramatically depending on the method used in the preceding step to create hypoxic conditions in the cell suspension, where a chemical agent, sodium dithionite, leads to reduction of cytochromes in addition to removal of dissolved oxygen, and bubbling-N 2 gas leads to displacement of dissolved oxygen only. These results have an impact on the assessment of experimental simulations of hypoxia in cells. The spectroscopic technique employed in this work will be used in the future as an analytical method to monitor the effects of varying levels of oxygen and nutrients supplied to cardiomyocytes during either the preconditioning of cells or the reperfusion of ischaemic tissue.

scholarly journals Assessing the Potential of Newly Isolated Pichia Fermentans for Xylitol Production Using Non-Detoxified Xylose Rich Pre-Hydrolysate Derived from Sugarcane Bagasse

2020 ◽  
Author(s):  
Ashish A Prabhu ◽  
Ekkarin Bosakornranut ◽  
Yassin Amraoui ◽  
Deepti Agarwal ◽  
Frederic Coulon ◽  
...  
Keyword(s):  
Sugarcane Bagasse ◽  
Type Strain ◽  
Shake Flask ◽  
Wild Type Strain ◽  
Xylose Reductase ◽  
Value Added ◽  
Xylitol Production ◽  
Wild Type ◽  
Conversion Yield ◽  
Cell Factories

Abstract Background: Integrated management of hemicellulosic fraction and its economical transformation to value-added products is the key driver towards sustainable second-generation biorefineries. In this aspect microbial cell factories are harnessed for sustainable production of biochemicals by valorising C5 and C6 sugars generated from agro-industrial waste. However, most of the strains can effectively consume C6 sugars but lacks pentose metabolism pathway. The effective utilization of both pentose and hexose sugars is key for economical biorefinery. Results: In the current study, the ability of a newly isolated xylose assimilating Pichia fermentans was explored for xylitol production. The wild type strain robustly grew on xylose and produced xylitol with >40% conversion yield. Mutagenesis with ethyl methanesulphonate (EMS) yielded seven mutants. The mutant obtained after 15 min exposure, exhibited best xylose bioconversion efficiency. This mutant under shake flask conditions produced maximum xylitol titre and yield of 34.0 g/L and 0.68 g/g, respectively. oweverHoHHHoHowever, under same conditions, the control wild type strain accumulated 27.0 g/L xylitol with a conversion yield of 0.45 g/g. Improved performance of the mutant was attributed to 34.6% activity enhancement in xylose reductase with simultaneous reduction of xylitol dehydrogenase activity by 22.9%. Later, the culture medium was optimized using statistical design and validated at shake flask and bioreactor level. Bioreactor studies affirmed the competence of mutant in xylitol accumulation. The xylitol titre and yield obtained with pure xylose were 98.9 g/L and 0.67 g/g, respectively while xylitol produced using non-detoxified xylose rich pre-hydrolysate from sugarcane bagasse was 79.0 g/L with an overall yield of 0.54 g/g. Conclusion: This study established the potential of P. fermentans in successfully valorising the hemicellulosic fraction for sustainable xylitol production.

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