Invertase immobilization onto radiation-induced graft copolymerized polyethylene pellets

Highly efficient production of inverted syrup in an analytical column with immobilized invertase

This paper presents a procedure by which a simple and economical analytical column containing immobilized invertase was developed. This column has high efficiency of converting sucrose into inverted syrup rapidly. Gelatine beads were used for the immobilization of invertase. The enzyme was entrapped efficiently and was found to be stable and retained its activity over a period of 3 months. Immobilization parameters for maximum enzyme activity were estimated as temperature optima at 60 °C, pH optima 7.0 and 30 mg/mL enzyme concentration was found to give maximum immobilization (72 %). The reusability of the gelatine immobilized invertase was found to be seven times with a time interval of 24 h. The immobilized invertase presented a KM of 51.28 mM and Vmax of 0.334 mM/min. The time required to hydrolyse 50 % sucrose solution by a column of length 10 cm and diameter of 1.5 cm was found to be 15 min at room temperature. The column was found effective for inversion of biological samples like sugar cane juice.

Invertase, glucose oxidase and catalase for converting sucrose to fructose and gluconic acid through batch and membrane-continuous reactors

Conversion of sucrose into fructose and gluconic acid using invertase, glucose oxidase and catalase was studied by discontinuous (sequential or simultaneous addition of the enzymes) and continuous (simultaneous addition of the enzymes in a 100 kDa-ultrafiltration membrane reactor) processes. The following parameters were varied: concentration of enzymes, initial concentration of substrates (sucrose and glucose), pH, temperature and feeding rate (for continuous process). The highest yield of conversion (100%) was attained through the discontinuous (batch) process carried out at pH 4.5 and 37 ºC by the sequential addition of invertase (14.3 U), glucose oxidase (10,000 U) and catalase (59,000 U).

Kinetics study of invertase covalently linked to a new functional nanogel

Nanogels are promising materials as supports for enzyme immobilization. A new hydrogel comprising of methacrylic acid (MAAc) and N-vinyl pyrrolidone (N-VP) and ethyleneglycol dimethacrylate (EGDMA) was synthesized and converted to nanogel by an emulsification method. Nanogel was further functionalized by Curtius azide reaction for use as support for the covalent immobilization of invertase (Saccharomyces cerevisiae). As-prepared or invertase-immobilized nanogel was characterized by FTIR, XRD, TEM and nitrogen analysis. The characterization of both free and the immobilized-invertase were performed using a spectrophotometric method at 540 nm. The values of V(max), maximum reaction rate, (0.123 unit/mg), k(m), Michaelis constant (7.429 mol/L) and E(a), energy of activation (3.511 kj/mol) for the immobilized-invertase are comparable with those of the free invertase at optimum conditions (time 70 min, pH 6.0 and temperature 45°C). The covalent immobilization enhanced the pH and thermal stability of invertase. The immobilized biocatalyst was efficiently reused up to eight cycles.

Immobilization of invertase in conducting copolymers of 3-methylthienyl methacrylate

Immobilization of invertase in conducting copolymer matrices of 3-methylthienyl methacrylate with pyrrole and thiophene was achieved by constant potential electrolysis using sodium dodecyl sulfate (SDS) as the supporting electrolyte. Polythiophene (PTh) was also used in entrapment process for comparison. Kinetic parameters, Michaelis-Menten constant, K(m), and the maximum reaction rate, V(max), were investigated. Operational stability and temperature optimization of the enzyme electrodes were also examined.

Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii

The production of xylitol from concentrated synthetic xylose solutions (S(o) = 130-135 g/L) by Debaryomyces hansenii was investigated at different pH and temperature values. At optimum starting pH (pH(o) = 5.5), T = 24 degrees C, and relatively low starting biomass levels (0.5-0.6 g(x)/L), 88% of xylose was utilized for xylitol production, the rest being preferentially fermented to ethanol (10%). Under these conditions, nearly 70% of initial carbon was recovered as xylitol, corresponding to final xylitol concentration of 91.9 g(P)/L, product yield on substrate of 0.81 g(P)/g(S), and maximum volumetric and specific productivities of 1.86 g(P)/L x h and 1.43 g(P)/g(x) x h, respectively. At higher and lower pH(o) values, respiration also became important, consuming up to 32% of xylose, while negligible amounts were utilized for cell growth (0.8-1.8%). The same approach extended to the effect of temperature on the metabolism of this yeast at pH(o) = 5.5 and higher biomass levels (1.4-3.0 g(x)/L) revealed that, at temperatures ranging from 32-37 degrees C, xylose was nearly completely consumed to produce xylitol, reaching a maximum volumetric productivity of 4.67 g(P)/L x h at 35 degrees C. Similarly, both respiration and ethanol fermentation became significant either at higher or at lower temperatures. Finally, to elucidate the kinetic mechanisms of both xylitol production and thermal inactivation of the system, the related thermodynamic parameters were estimated from the experimental data with the Arrhenius model: activation enthalpy and entropy were 57.7 kJ/mol and -0.152 kJ/mol x K for xylitol production and 187.3 kJ/mol and 0.054 kJ/mol x K for thermal inactivation, respectively.