The optimal conditions required for chitinase production from Bacillus licheniformis B307 strain, obtained from Syrian soil, were studied. Optimization experiments were carried out under submerged fermentation conditions, and colloidal chitin was the source of carbon. Luria broth medium supplied with 0.5% colloidal chitin was the optimum medium for chitinase production. The maximum chitinase yield was obtained at 30 C, pH6, incubation time 14 days, and 150 rpm. The optimum chitinase activity was achieved at 60 C and pH6. The chitinase activity with unmodified medium was 1.9 U/mL which then enhanced about eight folds to reach 14.2 U/mL under optimized submerged fermentation conditions. An extracellular chitinase of Bacillus licheniformis B307 was partially purified using ammonium sulfate precipitation followed by concentration with various sizes of concentrator tubes. The chitinase was partially purified 8.24 fold and specific enzyme activity increased 2.08 fold (2 U/mg). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of partial purified chitinase exhibited a molecular weight (M r ) near to 36 and 42kDa. These results make it possible to invest in this strain to produce chitinase to be used as antifungal, food additives and other applications.
-Penicillium canescens 10-10c strain was cultivated on barley straw hydrolysate as a soluble nutrient source and as inducer for xylanase production. Barley straw hydrolysate was obtained by treatment of barley straw with NaOH or hot water. In shake flask cultures, NaOH treatment was found to increase the biomass production, but was not accompanied by an increase in xylanase production. The best xylanase production (54 U/ml) was observed on hydrolyzed extract from barley straw treated with hot water (100 ºC) for 3 hours. Enzyme production was further improved by scaling up the cultivation process to a 3-L stirred tank bioreactor. For batch cultivations in the bioreactor, the maximum xylanase productivity reached 1.31 and 0.46 U/ml/h, respectively, after 96 and 168 hours of cultivation. However, xylanase productivity reached 3.46 U/ml/h in the continuous culture. These results suggest that xylanase can be produced efficiently by Penicillium canescens 10-10c in continuous culture from an inexpensive source such as barley straw hydrolysate.
Industrial important enzymes have traditionally been obtained by using submerged fermentation technology. Many organisms are able to produce these enzymes, but only a few of them exhibit satisfactory characteristics for industrial application. The ability of bacterial strains from the genus Bacillus to secrete large amounts of extracellular a-amylase has made them well suited for commercial production. Amylase production using Bacillus subtilis SY134D strain was conducted in flasks and bioreactor. In flasks, our results showed that soybean cake, beet pomace and tomato pomace were the best carbon source used in submerged fermentation (SmF) after 72 h of incubation. In bioreactor, the rates of air flow and agitation speed are important factors that affect oxygen transfer rate which influence on product formation. When the aeration rate was increased from 0.25 to 0.75 vvm, amylase production increased at the speed of agitation 100 and 200 rpm. The best enzyme yield 127 IU/mL was obtained at 0.25 vvm an aeration rate and 300 rpm agitation speed in a 3L Electro-lab bio-reactor.
Xylanase plays an important role in the food, feed, and pulp/paper industry. Filamentous fungi have been considered as useful producers of this enzyme from an industrial point of view, due to the fact that they excrete xylanases into the medium. In this study, four fungal species belonging to different genera, i.e. Aspergillus, Cochliobolus, Pyrenophora, and Penicillium were isolated from different sources and compared for their ability to produce xylanase in submerged culture. The fungal species showed enzyme activity as determined by dinitrosalicylic acid (DNS) method. It was found that the two saprophytic Aspergillus strains, i.e A. terreus (Fss 129) and A. niger (SS7) had the highest xylanase activity of 474 and 294 U ml–1 at pH 7 and 8, respectively, in the presence of corn cob hulls after 120 h of incubation. The production of xylanase seemed to be strongly influenced by the interactive effect of initial pH on the fungi. Interestingly, xylanase was better produced by the saprophytic fungi of Aspergillus and Penicillium than by the plant pathogenic ones of Cochliobolus and Pyrenophora. This work provides additional information to support future research on fungi with different lifestyles for food industrial production of xylanase.
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