Department of Biochemistry, Kurukshetra University, Kurukshetra, 136119 Haryana India.
Department of Microbiology, Kurukshetra University, Kurukshetra, 136 119 India.
J Food Sci Technol. 2014 Sep;51(9):1737-49. doi: 10.1007/s13197-014-1268-z. Epub 2014 Feb 4.
This study was conducted to evaluate the efficacy of purified free and immobilized xylanase in enrichment of fruit juices. Extracellular xylanase produced from Bacillus pumilus VLK-1 was purified to apparent homogeneity by 15.4-fold with 88.3 % recovery in a single step using CM-Sephadex C-50. Purified xylanase showed a single band on SDS-polyacrylamide gel with a molecular mass of 22.0 kDa. The purified enzyme was immobilized on glutaraldehyde-activated aluminum oxide pellets and the immobilization process parameters were optimized statistically through response surface methodology. The bound enzyme displayed an increase in optimum temperature from 60 to 65 ºC and pH from 8.0 to 9.0. The pH and temperature stability of the enzyme was also enhanced after immobilization. It could be reused for 10 consecutive cycles with 58 % residual enzyme activity. The potential of purified xylanase (free and immobilized) in juice enrichment from grape (Vitis amurensis) and orange (Citrus sinensis) pulps has been investigated. The optimization of this process using free xylanase revealed maximum juice yield, clarity and reducing sugar on treatment with 20 IU/g fruit pulp for 30 min at 50 ºC. Treatment of both the fruit pulps with xylanase under optimized conditions resulted in an increase in juice yield, clarity, reducing sugars, titratable acidity, and filterability but a decline in turbidity and viscosity. Immobilized enzyme was more effective in improving juice quality as compared to its soluble counterpart. The results showed B. pumilus VLK-1 xylanase, in both free and immobilized form, as a potential candidate for use in fruit juice enrichment.
本研究旨在评估纯化的游离和固定化木聚糖酶在果汁增稠中的功效。从解淀粉芽孢杆菌 VLK-1 中产生的胞外木聚糖酶通过 CM-Sephadex C-50 在单一步骤中进行了 15.4 倍的纯化，回收率为 88.3%，达到明显的均一性。纯化的木聚糖酶在 SDS-聚丙烯酰胺凝胶上显示出一条带，分子量为 22.0 kDa。纯化的酶通过戊二醛活化的氧化铝小球固定化，通过响应面法对固定化过程参数进行了统计学优化。固定化酶的最适温度从 60°C 增加到 65°C，pH 值从 8.0 增加到 9.0。固定化后，酶的 pH 值和温度稳定性也得到了提高。它可以连续使用 10 次，残留酶活为 58%。从葡萄（山葡萄）和橙子（甜橙）果肉中提取果汁时，已研究了纯化的游离和固定化木聚糖酶的潜力。使用游离木聚糖酶优化此过程，在 50°C 下处理 30 分钟，每克果肉用 20 IU/g 木聚糖酶，可获得最大的果汁产量、澄清度和还原糖。在优化条件下，两种水果果肉均用木聚糖酶处理，可提高果汁产量、澄清度、还原糖、可滴定酸度和过滤性，但浊度和粘度降低。与可溶性酶相比，固定化酶在改善果汁质量方面更为有效。结果表明，解淀粉芽孢杆菌 VLK-1 木聚糖酶无论是游离形式还是固定化形式，都是果汁增稠的潜在候选酶。
