Pročišćavanje i karakterizacija endoinulinaze iz mutanta bakterije Xanthomonas campestris pv. phaseoli KM 24

An extracellular endoinulinase from Xanthomonas campestris pv. phaseoli KM 24 mutant was purifi ed to homogeneity by gel fi ltration chromatography and showed a specifi c activity of 119 U/mg. The optimum pH and temperature of the purifi ed enzyme were found to be 6.0 and 50 °C, respectively. The enzyme was stable up to 60 °C, retaining 60 % of residual activity for 30 min, but inactivated rapidly above 60 °C. The enzyme was found to be stable at pH=6–9 when it retained 100 % of its residual activity. The Lineweaver-Burk plot showed that the apparent Km and vmax values of the inulinase when using inulin as a substrate were 1.15 mg/mL and 0.15 μM/min, respectively, whereas the kcat value was found to be 0.145 min–1. The calculated catalytic effi ciency of the enzyme was found to be 0.126 (mg·min)/mL. The purifi ed inulinase can be used in the production of high fructose syrups.Iz mutanta bakterije Xanthomonas campestris pv. phaseoli KM 24 izolirana je izvanstanična endoinulinaza, te je pročišćena gel-filtracijskom kromatografijom. Specifična aktivnost bila je 119 U/mg. Optimalna pH-vrijednost za aktivnost pročišćenog enzima bila je 6,0 a temperatura 50 °C. Enzim je bio stabilan na temperaturama manjim od 60 °C, zadržavajući 60 % aktivnosti tijekom 30 min, ali se iznad 60 °C naglo inaktivirao. Pri pH- -vrijednosti od 6 do 9 enzim je zadržao 100 % aktivnosti. Pomoću Lineweaver-Burk-ovog dijagrama utvrđeno je da je na podlozi s inulinom Km vrijednost inulinaze bila 1,15 mg/mL a vmax 0,15 μg/mL, dok je kcat vrijednost iznosila 0,145 min-1. Katalitička je aktivnost enzima bila 0,126 (mg·min)/mL. Zaključeno je da se pročišćena se inulinaza može primijeniti za proizvodnju sirupa s velikim udjelom fruktoze

An industrial perspective of factors affecting molasses fermentation by Saccharomyces cerevisiae

In this study, an effort has been made to address the key issue of how molasses quality and composition are key components for higher yields during ethanol fermentation. Moreover, it was also noted that the choice of a yeast strain and yeast preconditioning have a positive effect on alcohol yield during molasses fermentation. A considerably better alcohol yield (9%) was obtained with low residual sugars (< 0.3%), and an increased glycerol concentration from 0.5 to 0.9%. Microbiological analysis revealed a total aerobic count (TAC) of 1.18 × 10 6 cfu/ml and Lactobacilli count of 8.4 × 10 5 cfu/ml after 22 h fermentation on de Man, Rogosa and Sharpe (MRS) agar media. The wild yeast count was relatively high reaching 9 × 10 2 cfu/ml within 40 min of commencement of the fermentation but decreased to 3 × 10 4 cfu/ml after 22 h of fermentation. This study has shown some of the possible causes of poor fermentation and advantages of cell preconditioning in molasses fermentation by Saccharomyces cerevisiae