Green Synthesis of Porous Spherical Reduced Graphene Oxide and Its Application in Immobilized Pectinase.

Pectinase is widely used in juice production, food processes, and other fields. However, owing to poor stability, free pectinase is difficult to separate from a substrate after hydrolysis and cannot be reused, and thus its industrial use is limited. Immobilized pectinase can solve these problems well. We prepared a carrier material of immobilized enzyme, which is called porous spherical reduced graphene oxide (rGO) with a rich pore structure, large specific surface area, strong hardness, and good biocompatibility to enzyme. Then, we evaluated the performance of the porous spherical rGO immobilized pectinase and characterized its structure by IR, XRD, and SEM. Using this material as a carrier of immobilized enzyme improves the load and catalytic activity of the enzyme. After 10 times of continuous use, the porous spherical rGO immobilized enzyme still maintained its initial relative enzyme activity at around 87%, indicating that immobilized pectinase had a stronger cycling stability, and its thermal stability, acid-base tolerance, and storage stability were superior to those of free pectinase. The results were compared with those of other studies on immobilized pectinase. The relative activity of pectinase immobilized by porous spherical rGO was at a high level after 10 consecutive uses. Overall, the spherical rGO is an excellent immobilized enzyme carrier material.

Immobilization of Pectinase onto Porous Hydroxyapatite/Calcium Alginate Composite Beads for Improved Performance of Recycle.

Pectinase is an industrially important enzyme widely used in juice production, food processing, and other fields. The use of immobilized enzyme systems that allow several reuses of pectinase is beneficial to these fields. Herein, we developed mechanically strong and recyclable porous hydroxyapatite/calcium alginate composite beads for pectinase immobilization. Under the optimal immobilization parameters of 40 °C, pH 4.0, 5.2 U/L pectinase concentration and 4 h reaction time, pectinase showed the highest enzymatic activity (8995 U/mg) and immobilization yield (91%). The thermal stability and pH tolerance of the immobilized pectinase were superior to those of free pectinase. The storage stability of the free and immobilized pectinase for 30 days retained 20 and 50% of their initial activity, respectively. Therefore, these composite beads might be promising support for the efficient immobilization of industrially important enzymes.

Synthesis and characterisation of galactosyl glycerol by ß-galactosidase catalysed reverse hydrolysis of galactose and glycerol.

A study of an enzymatic method for the production of galactosylglycerol is described. The effects of enzyme sources, enzyme amount, reaction temperature, reaction time, substrate ratio of glycerol to galactose, buffer content and pH on galactosylglycerol yield (mg/ml) were investigated. Under the optimum reaction conditions of ß-galactosidases from Kluyveromyces lactis 240 U/ml, temperature 40 °C, time 24 h, buffer amount 60% (percent volume of buffer to that of substrates, pH 6.5), and the substrate molar ratio of 10 (glycerol16 mmol:galactose 1.6 mmol), the yield of galactosylglycerol was up to 116.47 mg/ml (galactose conversion 55.88%). The product was purified by activated charcoal and Sephadex G-15 column chromatography, up to 96%. The purified galactosylglycerol was fully characterised by MS and NMR, and identified as a mixture of (2R)- and (2S)- 3-O-ß-D-galactopyranosyl-glycerol.