Extraction and quantification of proteins from shrimp shell waste using green solvents
Abstract:
The aim of this thesis was the selective extraction of proteins from shrimp shell waste using environmentally friendly (green) solvents. 19 solvents were prepared: Milli-Q water, three buffers at pH 7 (phosphate, McIlvaine and phosphate buffered saline) and 15 deep eutectic solvents based on choline chloride or betaine containing 15 wt.% water. Four of the deep eutectic solvents had solidified at room temperature, so 15 solvents were tested in solid–liquid extraction (solid-liquid ratio of 0,2, 25 °C, 300 rpm, 30 min). The protein content of the supernatants was determined by UV-Vis spectroscopy at 280 nm using a bovine serum albumin calibration curve, and the extraction of astaxanthin was monitored at the absorbance of 482 nm. The total extractable protein content from the the biomass, determined by six consecutive extraction cycles with McIlvaine buffer pH 7, was 45,0 mg/g of shells. The highest single cycle extraction efficiencies were obtained with deep eutectic solvents of betaine:propionic acid (94,6 %) and choline chloride:malonic acid (93.6 %), however, both also extracted astaxanthin. The deep eutectic solvent of betaine:acetic acid, which combined a high efficiency of extraction (68,4 %), with negligible astaxanthin extraction, was therefore identified as the most suitable selective green solvent.
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