Date

2014

Author

Uzuner, Sibel

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Utilization of cheap and abundant materials for enzyme production is one of the strategies that can reduce the product costs. Besides, use of renewable agro-food industrial wastes as a raw material provides not only low cost and sustainable value added products but also is a solution to waste disposal problem.In this study, fermentation medium composition and conditions for maximal production of pectinase enzyme from Bacillus subtilis in submerged fermentation were investigated. The potential use of crude enzyme for clarification of carrot juice was also evaluated. In order to enhance utilization of the hazelnut shells as carbon source in pectinase production, various pretreatment methods including dilute acid, alkaline, and ozone pretreatments were tested prior to enzymatic hydrolysis step.After conversion of hazelnut shells to fermentable sugars, the “Plackett-Burman”(PB) design was used for screening of the eight factors; pH, fermentation time,temperature, inoculum volume (%v/v) and of pectin, yeast extract (YE),magnesium sulphate [MgSO4], and dipotassium hydrogen phosphate [K2HPO4]. Five variables (pH, time, temperature, yeast extract concentration and K2HPO4), which were determined to be significant by PB design, were further optimized using Box-Behnken response surface method to maximize the PG activity.The produced crude enzyme was tested in clarification of carrot juice, highly nutritious and worldwide consumed food material, afterwards. The carrot juice was treated with different concentration of crude pectinase (0.1-0.5%), pH (4-7), and time (2-6 h) for clarification.Among the pretreatment methods tested, the dilute acid pretreatment (3.42(w/w)%acid, 31.7 min, 130 oC) was chosen the best with higher sugar conversion (62.8% saccharification yield) than sodium hydroxide and ozone pretreatment methods.The pectinase optimization results indicated that a maximal PG activity of 5.60 U/mL was achieved at pH 7.0, 72 h, and 30 oC using 0.5% (w/v) of yeast extract and 0.02% (w/v) of K2HPO4. The results of clarification revealed that 100% clarity was achieved at 0.5% (w/v)enzyme load, 7.0 pH, and 6 h of clarification yield (%) with commercial enzyme reached only 78.18±3.14 %.This study also proved that crude enzyme was equally effective as the purified commercial enzyme.

Subject Keywords

Polygalacturonase., Enzymes., Carrots., Hazelnuts., Vegetable juices.

URI

http://etd.lib.metu.edu.tr/upload/12618355/index.pdf
https://hdl.handle.net/11511/24314

Collections

Graduate School of Natural and Applied Sciences, Thesis