Mathematical modeling of fructose production by immobilised glucose isomerase as a function of temperature and pH variations

Production of fructose from glucose isomerisation process using commercial immobilized glucose isomerase (IGI) was conducted in a batch type of stirred tank bioreactor. A mathematical model was developed to describe the effect of temperature and pH on the kinetic parameters of fructose production. Modified Santos model known as MM3 was used to describe this phenomenon. The influence of temperature and pH was investigated and quantified. The results showed that, even though the highest R2 was at 70°C but based on the IAE of 0.843 and ISE of 0.978, it proved that for enzymatic reaction, it should be carried out below 65°C. Effect of pH for various models have shown that, the IAE and ISE were less than one whereas the R2 were greater than 0.95. This indicates that the model, MM3 is acceptable.Keywords: Batch reactor, fructose, glucose isomerisation, mathematical modeling, pH, temperatur

Immobilization Strategy of Recombinant Xylanase from Trichoderma reesei by Cross-linked Enzyme Aggregates

Abstract—Modern developments in biotechnology have paved the way for extensive use of biocatalysis in industries. Although offering immense potential, industrial application is usually hampered by lack of operational stability, difficulty in recovery as well as limited re-use of the enzyme. These drawbacks however can be overcome by immobilization. Cross-linked enzyme aggregates (CLEAs), a versatile carrier-free immobilization technique is one that is currently capturing global interest. This approach involves precipitating soluble enzyme with an appropriate precipitant and subsequent crosslinking by a crosslinking reagent. Without ineffective carriers, CLEAs offer high enzymatic activity, stability and reduced production cost. This study demonstrated successful CLEA synthesis of recombinant xylanase from Trichoderma reesei using ethanol as aggregating agent and glutaraldehyde (2% (v/v); 100 mM) as crosslinker. Effects of additives including proteic feeder such as bovine serum albumin (BSA) and poly-L-Lysine were investigated to reveal its significance in enhancing the performance of enzyme. Addition of 0.1 mg BSA/U xylanase showed considerable increment in CLEA development with approximately 50% retained activity

Immobilization of recombinant escherichia coli on multi-walled carbon nanotubes for xylitol production

E. coli has been engineered to produce xylitol, but the production faces bottlenecks in terms of production yield and cell viability. In this study, recombinant E. coli (rE. coli) was immobilized on untreated and treated multiwalled carbon nanotubes (MWCNTs) for xylitol production. The immobilized rE. coli on untreated MWCNTs gave the highest xylitol production (5.47 g L−1) and a productivity of 0.22 g L−1 h−1. The doubling time for the immobilized cells increased up to 20.40 h and was higher than that of free cells (3.67 h). Cell lysis of the immobilized cells was reduced by up to 73 %, and plasmid stability improved by up to 17 % compared to those of free cells. Xylitol production using the optimum parameters (pH 7.4, 0.005 mM and 29 °C) achieved a xylitol production and productivity of 6.33 g L−1 and 0.26 g L−1 h−1, respectively. A seven-cycle repeated batch fermentation was carried out for up to 168 h, which showed maximum xylitol production of 7.36 g L−1 during the third cycle. Hence, this new adsorption immobilization system using MWCNTs is an alternative to improve the production of xylitol

High xylooligosaccharides (XOS) production from pretreated kenaf stem by enzyme mixture hydrolysis

Advancement in industrial biotechnology offers potential opportunities for economic utilization of agro-industrial biomass such as kenaf (Hibiscus cannabinus) for the production of value-added products. This work was conducted to evaluate an enzymatic hydrolysis of kenaf stem (that has been pretreated) for xylooligosaccharides (XOS) production. Pretreated kenaf stems were subjected to two enzymatic hydrolysis approaches which are single xylanase (Xyn2) and a mixture of xylanase:arabinofuranosidase (Xyn2:An. abfA). Central Composite Design was used to optimize the enzymatic hydrolysis conditions on the pretreated kenaf stem to achieve maximum hemicellulose conversion. Under the optimized hydrolysis conditions, hemicellulose conversion (95.03%) with the highest XOS yield of 351.46 mg/g was achieved at 40 °C (pH 4.0) after 48. h incubation with Xyn2:An. abfA ratio of 400. U:10. U. Xylobiose (135.42 mg/g) is the main XOS product with xylotriose (102.04 mg/g) being the second highest. The high production of XOS yield from the pretreated kenaf stem demonstrated the biotechnological potential of the kenaf in the future