جستجوی مقالات مرتبط با کلیدواژه "tannic acid" در نشریات گروه "زیست شناسی"

Tannins (tannic acid) are toxic, high molecular weight and water- soluble polyphenols that are present in many plants such as pistachio and its by- products. Wide ranges of microorganisms including bacteria tolerate tannin and degrade it. The aim of this study was to isolate and characterize tannin- tolerant bacteria from pistachio soft hulls (P- SH) and feces of goat before and after feeding on this by- product as tannin rich diet.
Tannin tolerant bacteria were isolated from enrichment cultures of samples in medium containing tannic acid as a sole source of carbon and energy. Tannin hydrolyzing ability of isolates was confirmed by observation of clear zones around the colonies. The increasing concentrations of tannin on minimal salt medium (MSM) agar plates were used to test the maximum tolerable concentrations (MTCs). Furthermore, in the supplemented media tannin concentrations were measured by bovine serum albumin (BSA) precipitation assay during time intervals.
Tannin- degrading bacterial population of P- SH was about only 10.3% of total population. More than 50 percent of tannin degrading strains were isolated from goat feces after grazing on tannin rich diet. Isolated bacteria were Gram- negative and positive rod species belonging to Klebsiella, Pseudomonas, Bacillus, Escherichia and Enterobacter genera. Among the isolated bacteria 71.4% could tolerate the concentration of 64 g/l of tannin in their media while only 7.2% were able to tolerate the maximum tannin concentration of 16 g/l. Bacterial isolates of goat feces could degrade tannin more than 72% after 72 h of incubation. In the case of soft P- SH isolates, the biodegradation percentage was between 17- 75%.
Discussion and Feeding of tannin rich diet induced a shift in digestive system microbial profile with increased population of tannin tolerant bacteria. The ability of isolated strains provides novel insights for the role they can play in composting tannin containing wastes.

Tannase can be obtained from the various sources for example tannin rich plants; however microbial sources are preferred for industrial production. In microbial sources, the Aspergillus and Penicillium genus and lactic acid bacteria mostly produce tannase. However, it has been identified that this enzyme is produced by many fungi and bacteria, but researches are continuing to find new species.. The aim of this study was to isolate a tannase-producing fungi from moldy tea leaves and to study some properties of its enzyme.. The present study was done via two steps. At first, industrially important tannaseproducing fungi were isolated from moldy tea leaves using the simple agar plate method followed by the screening of organisms capable of producing tannase using the enrichment culture technique in modified Czapek Dox’s agar. Finally, tannase obtained from the best isolate was partially purified and characterized.. Tannase produced by Penicillium sp. EZ-ZH190 isolated from moldy tea leaves was partially purified and characterized. Maximum enzyme production (4.33 U.mL-1) was recorded after 96 hours of incubation at 30 °C in submerged culture (100 rpm) utilizing 1% (w/v) tannic acid as a sole carbon source. This tannase exhibited optimum activity at 35 °C and at pH of 5.5, and showed nearly 50% of its maximal activity at 50 °C. In the present study, tannase from Penicillium sp. EZ-ZH190 had KM and Vmax values of 1.24 mM and 17.09 U.mL-1, respectively, and showed more than 50% stability at salt (NaCl) concentration of 1 M for 24 hours.. Tannase productivity of Penicillium sp. EZ-ZH190 (0.045 U.mL-1.h-1) is comparable with the maximum tannase productivity in the reported literatures, and the biochemical characteristics showed by Penicillium sp. EZ-ZH190 tannase are considered favorable for tannin biodegradation in the industry. So, we concluded that Penicillium sp. EZ-ZH190 is a good strain for use in the efficient production of tannase..