مقایسه کاربرد صنعتی اگزوپلی ساکاریدهای دو سویه سیانوباکتری آبزی و خاکزی neowestiellopsis persica a1387 و nostoc punensis در تصفیه زیستی فلزات سنگین

مقدمه: تولید اگزوپلی‌ساکاریدها (eps) توسط سیانوباکتری‌ها در پاسخ به تنش فلزات سنگین یکی از ویژگی‌های مهم این میکروارگانیسم‌ها در تصفیه زیستی آب‌های آلوده است. در این پژوهش، توانایی دو سیانوباکتری خاک‌زی و آب شیرین nostoc punensis و neowestiellopsis persica a1387 در حذف فلزات سنگین کروم، نیکل و مس بررسی شده است.مواد و روش‏‏ها: پس از رشد سیانوباکتری‌های nostoc punensis و neowestiellopsis persica a1387 در محیط کشت bg-110  در اتاقک رشد، تلقیح به محیط حاوی فلزات سنگین انجام شد. سپس میزان حذف فلزات سنگین در بازده زمانی 90 دقیقه‌ای به همراه اندازه‌گیری وزن خشک، کربوهیدرات، پروتئین و اگزوپلی‌ساکاریدها انجام شد. علاوه بر آن، آنالیز دستگاهی طیف‌سنجی تبدیل رامان و فوریه به مادون قرمز (ftir) و طیف‌سنجی جرمی - کروماتوگرافی گازی (gc-ms) به‌منظور شناسایی گروه‌های عاملی موثر و ترکیبات فرار موثر در حذف فلزات سنگین انجام شدند.نتایج: نتایج حاصل از آنالیز واریانی یک‌طرفه و آزمون توکی نشان دادند بیشترین میزان وزن خشک سلولی، اگزوپلی‌ساکارید، کربوهیدرات و پروتئین در سویه neowestiellopsis persica a1387 در مواجه فلزات نیکل و کروم یافت شد. علاوه بر آن، نتایج حاصل از جذب اتمیک فلزات سنگین نشان دادند سویه neowestiellopsis persica a1387، در ده دقیقه اول بیشترین میزان حذف فلز نیکل (350 میلی‌گرم بر وزن خشک) را نشان داد. نتایج حاصل از ftir نشان دادند در نواحی cm-1 405، cm-1 575 و cm-1 920-813 پیک‌هایی در ارتباط با گروه‌های خمشی c-n و کربونیل (c=o) یافت شدند که تنها مواجه با فلزات سنگین مشاهده شد. نتایج حاصل از مطالعات gc-ms نیز نشان دادند بیشترین فراوانی ترکیبات فرار butanal، acetic acid ethyl ester، 2-phenylethanol و 2,4-hexadienal در سیانوباکتری neowestiellopsis persica a1387 در تیمار با نیکل یافت شد.بحث و نتیجه‏ گیری: سیانوباکتری آبزی neowestiellopsis sp. مقاومت بیشتری نسبت به سیانوباکتری خاک‌زی nostoc sp. در تیمارهای فلزی (مس، نیکل و کروم) از خود نشان داد.

a comparison of industrial application of exopolysaccharides of two strains of aquatic and terrestrial cyanobacteria neowestiellopsis persica a1387 and nostoc punensis in bioremediation of heavy metals

introduction: the production of exopolysaccharides (eps) by cyanobacteria in response to heavy metal stress is one of the important features of these microorganisms in the biological treatment of polluted waters. cyanobacteria, as valuable resources in the production of exopolysaccharides, have distinctive features compared to other bacteria. these compounds are composed of a large number of different monosaccharides, most of which are polymers with 6–13 different sugars, which is in contrast to the polymers produced by other bacteria and microalgae. also, the exopolysaccharides of cyanobacteria usually contain two different uronic acids (glucuronic and galacturonic acid) and sulfate groups, which are not common in the exopolysaccharides of other bacteria. as a result, these properties make the exopolysaccharides of cyanobacteria very suitable for biotechnological applications such as removing heavy metals from polluted water or thickening or emulsifying agents. the presence of negative charges (urea acids) in the exopolysaccharides of cyanobacteria, which play an important role in the absorption of metal cations, is a potentially beneficial phenomenon for water purification. in this research, the ability of two soil and freshwater cyanobacteria, nostoc punensis and neowestiellopsis persica a1387, to remove heavy metals such as chromium, nickel, and copper has been investigated.materials and methods: the strains of nostoc punensis and neowestiellopsis persica a1387 cyanobacteria used in this research were obtained from the cyanobacteria culture collection of azad university, science and research unit, cyanobacteria culture collection (ccc). after the inoculation of heavy metals such as copper, chromium, and nickel, the concentrations of exopolysaccharide content, protein content, and carbohydrate produced by the two strains were investigated and compared with the control. in addition, gc-ms and ft-ir were used to check the amount of effective volatile compounds and functional groups involved in the removal of heavy metals. resultsthe effect of metals on dry weight and concentration of exopolysaccharides in a cyanobacterial strain: nostoc punensis was more sensitive to metal treatments and had a lower cell dry weight. the concentration of exopolysaccharide produced by neowestiellopsis persica a1387 was higher than that of nostoc punensis and produced more in a fixed time.the effect of protein and carbohydrate content on the removal of heavy metals: the results showed that the cyanobacterium nostoc punensis was the superior strain in protein production, and the neowestiellopsis persica a1387 was the superior strain for carbohydrate production.the results of the removal of heavy metals in the liquid culture of cyanobacteria strains: the results showed that the cyanobacterium neowestiellopsis persica a1387 was the superior strain in removing metals, and at a fixed time, it removed more metals compared to the cyanobacterium nostoc punensis.the results of gc-ms studies of cyanobacterial strains: the results of gc-ms studies showed that the highest frequency of volatile compounds butanal, acetic acid ethyl ester, 2-phenylethanol, and 2,4-hexadienal were found in the cyanobacterium neowestiellopsis persica a1387 in treatment with nickel.the results of examining exopolysaccharides using the ft-ir method: the results of ftir showed that in the regions of 405 cm-1, 575 cm-1 and 813-920 cm-1 peaks were found in connection with c-n and carbonyl (c=o) bending groups, which were observed only when exposed to heavy metals.discussion and conclusion: the final result of this study showed that the highest amount of cell dry weight in the control was related to nostoc sp., but in the face of heavy metals, the neowestiellopsis persica a1387 strain had the highest cell dry weight in nickel and chromium metals. on the other hand, the highest amount of exopolysaccharide, carbohydrate, and protein in the control is related to the neowestiellopsis persica a1387 strain, but when faced with heavy metals, the neowestiellopsis persica a1387 strain had the highest amount of exopolysaccharide, carbohydrate, and protein in nickel metal. a study of heavy metal absorption by atoms also showed that the neowestiellopsis persica a1387 strain removed nickel metal more quickly than the nostoc punensis strain in the first ten minutes. the results of raman and fourier transform spectroscopy techniques in this research showed that the cyanobacterium neowestiellopsis persica a1387 showed more resistance than the cyanobacterium nostoc punensis to metal treatments. the superior strain for removing heavy metals was the cyanobacterium neowestiellopsis persica a1387. regarding the cyanobacterium neowestiellopsis persica a1387, a peak was seen in the region of 405 cm-1 of the control strain, which was related to the c-n bending group. this peak was found only in the strain treated with copper. in the region of 575 cm-1 of the control strain and the strains treated with chromium and nickel, a peak related to the carbonyl bending group (c=o) was observed, but this peak was changed in the strain treated with copper. the peaks in the range of 1000 cm-1 are related to c-o groups of polysaccharide and sugar skeleton, which were seen in all treatments of neowestiellopsis persica a1387 and the control strain. the peaks of the strain treated with copper in the range of 1115–1048 cm-1 were related to the strong pull of po43- and nh3+, which is related to the sugar skeleton and anomeric c-o-c and c-o groups of sugars. in the regions of 1654 cm-1 and 2935 cm-1, the peak corresponding to the stretching carbonyl group and stretching n-h and oh did not show any changes.