Extractive disruption process integration using ultrasonication and aqueous two-phase system for protein recovery from microalgae / Phong Win Nee

Phong , Win Nee (2017) Extractive disruption process integration using ultrasonication and aqueous two-phase system for protein recovery from microalgae / Phong Win Nee. Masters thesis, University of Malaya.

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Abstract

Microalgae emerge as the most promising protein source for aquaculture industry. However, the commercial production of microalgal protein at low cost remains challenging. The release of protein from microalgae is restricted by the presence of rigid thick cell wall. Another technical hurdle is that the whole protein recovery process involves several steps such as cell disruption, isolation and extraction; which is generally complicated, time-consuming and costly. To solve the technical hurdles, two experiments were designed in this study. The first experiment focused on the evaluation of a simple, economic, practical and scalable cell disruption technique for the protein recovery from microalgae. The effects of solvent types, alkali, and ultrasonication in cell disruption and protein solubility of microalgae (Chorella sorokiniana, Chorella vulgaris, Chlamydomonas sp. Tai-03 and Scenedesmus sp. Esp-07) were studied. To date, the notion of integrating microalgal cell disruption and protein recovery process into one step is yet to explore. Therefore, the feasibility of applying methanol/potassium ATPS in the extractive disruption integrated process for protein recovery was investigated in the second experiment. Parameters such as salt types, salt concentrations, methanol concentrations, NaCl addition were optimized. The possibility of upscaling and the effectiveness of using the recycled phase components at each recycling step were also studied. Based on the findings from the first experiment, it was found that alkaline treatment played a key role in cell disruption and protein solubilisation. From the industrial perspective, water is an excellent choice of solvent for simultaneous cell disruption and protein solubilisation due to low cost, ubiquitous availability and scalability. The combination of both alkaline and ultrasonication treatment showed the highest percentage of protein release and was thus proposed to be suitable for industrial application. The protein concentrations obtained from all the four microalgal strains after treated with the combination treatment were about 15-30% higher than alkaline treatment and about 27-261% higher than ultrasonication treatment when using water as the solvent. Protein-rich strain of C. sorokiniana was selected for further study in the second experiment. The disruption method used in the second experiment was the combination of alkaline and ultrasonication treatment. Based on the results obtained from the integrated process, it was found that ATPS formed by 30% (w/w) K3PO4 and 20% (w/w) methanol with 3% (w/w) NaCl addition was optimum for protein recovery. In this system, the partition coefficient and yield were 7.28 and 84.23%, respectively. There were no significant differences in the partition coefficient and yield when the integrated process was scaled up to 100-fold. The recycled phase components can still be performed effectively at the 5th cycle. In conclusion, the findings suggested that the integrated process is simple, environmental friendly and could be implemented at large scale.

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