تهیه بیوپلیمر بر پایه آگار استخراج شده از جلبک قرمز acanthophora خلیج فارس و ارزیابی خواص آن

در میان پلیمرهای زیستی مختلف مورد استفاده برای تهیه فیلم‌، پلی‌ساکاریدها به دلیل فراوانی و غیر سمی بودن به عنوان اجزای اصلی فیلم به‌شمار می‌آیند. مخلوط آگار با سایر پلیمرها مانند pva، خواص مکانیکی و زیست تخریب‌پذیری کامپوزیت‌های زیستی بهبود می‌بخشد. هدف اصلی این پژوهش ساخت بیوپلیمر به منظور کاربرد در صنایع بسته‌بندی با آگار استخراج شده از ماکروجلبک acanthophora در ترکیب با پلیمر صنعتی پلی‌ونیل‌الکل و گلیسرول است. برای ساخت بیوپلیمر آگار، در ابتدا بهینه‌سازی استخراج پلیمر آگار از ماکروجلبک با روش سدیم هیدروکسید/ گرمادهی انجام ودر مرحله بعد سنجش ترکیبات محلول آگار استخراجی صورت گرفت. سپس برای ساخت کامپوزیت زیستی با روش قالب‌گیری از گلیسرول (30 درصد وزنی-وزنی) و پلیمر pva (25 درصد وزنی-وزنی) استفاده شد. نتایج نشان داد که بازده استخراج برای روش پیش‌تیمار سدیم هیدروکسید/گرمادهی 15 درصد است. آزمون سنجش میزان کل ترکیبات فنلی محلول آگار استخراج شده نشان داد که میزان ترکیبات فنولی محلول آگار 0.004 ± 0.077 بر حسب میلی‌گرم اسید گالیک/ گرم آگار و میزان پروتئین محلول آگار استخراج شده، حاوی 0.019 ± 0.040 پروتئین بر حسب میلی‌گرم/میلی‌لیتر آگار است. نتایج آزمون کشش بیانگر این بود که افزودن گلیسرول به آگار باعث افزایش انعطاف‌پذیری و افزودن پلیمر pva باعث افزایش در میزان استحکام کششی و بهبود خواص فیزیکی نظیر افزایش درجه تورم، کاهش درصد حلالیت در آب فیلم‌های زیستی برپایه آگار می‌شود. در نهایت نتایج، استفاده از این پوشش‌ها جهت بسته‌بندی میوه و سبزیجات در مناطق گرمسیری با افزایش طول عمر مفید آن‌ها به مدت حداقل تا 5 روز در دمای 25 درجه سانتی‌گراد تایید می‌کند.

preparation of biopolymer based on agar extracted from persian gulf red algae acanthophora and evaluation of its properties

introduction  consumer demand for healthy food free of chemical preservatives and environmental concerns with plastic packaging environments are analyzed, which can be replaced by aquatic environments that can be contaminated, for the development of bio-based packaging materials. natural polymers have the ability to be biodegradable due to the presence of oxygen or nitrogen atoms in their main polymer chain compared to the dominant carbon-carbon bonds in fossil-based polymers. among the various biopolymers used to prepare multilayer films, polysaccharides are considered as the main components of the film due to their abundance and non-toxicity. these films generally have good mechanical strength, moderate physical properties, and most importantly, are edible and easily degradable. however, they are very brittle and hydrophilic, and these properties are undesirable in food packaging applications. among polysaccharides, agar, commercially extracted from seaweed, is one of the most common and widely studied base materials. agar is insoluble in cold water, but soluble in water at 90-100°c. when making an agar film, the solution and casting surface must be kept above the agarose gel setting temperature to avoid premature gelation. compared to other biopolymers, agar is more stable at low ph and high temperature. this thermoplastic and biocompatible polysaccharide creates films with high mechanical strength, transparency and moderate barrier properties to carbon dioxide and oxygen, and most importantly, it is edible and easily biodegradable. mixing agar with other polymers such as polyvinyl alcohol (pva) and polyethylene improves the mechanical, thermal and biodegradability properties of bio composites. the main goal of this study is to make biofilms for use in packaging industries with agar polymer extracted from macroalgae species acanthophora sp. agar was extracted by sodium hydroxide/heating method and the film was prepared in combination with industrial polymer pva and glycerol. materials and methods  to make biofilms based on agar polymer, firstly, optimization of agar polymer extraction from macroalgae species acanthophora sp. was done by sodium hydroxide/heating method, and in the next step, total phenolic compounds and the amount of soluble protein in extracted agar were measured. in the next step, glycerol with 30% by weight was used as a softener and pva polymer with a weight ratio of 25% to the dry weight of agar powder was used to make bio composite by solvent casting method, in order to strengthen the mechanical and physical properties of bio composites. characterization tests of the prepared composites included: xrd, ftir and tensile test. laboratory tests include; the percentage of solubility in water and degree of swelling for all bio-composites were evaluated to determine the optimal physical properties of bio-films.results and discussion:he results showed that; 15% extraction efficiency was obtained for sodium hydroxide/heating pretreatment method. the results of measuring the amount of total phenolic compounds in agar solution extracted by sodium hydroxide/heating method showed that the number of phenolic compounds in agar solution was 0.077 ± 0.004 in terms of mg of gallic acid/g of agar. the results of measuring the amount of protein in extracted agar determined by bradford method showed that the agar solution contains 0.040 ± 0.019 mg/ml of protein. a decrease in the swelling rate and an increase in the water solubility of the agar bio composite occurred with the addition of glycerol and pva polymer. the results of the tensile test showed that the addition of glycerol, a small hydrophilic molecule, to the agar bio composite leads to a decrease in the elastic modulus and an increase in flexibility.