Protein extraction from carbohydrate-digested rice and algae and the effects of amino acid mixtures on myotube differentiation

Abstract

The aim of this thesis is to assess the potential of non-animal protein sources from carbohydrate-digested rice (CDR), the rice by-product from sports drinks production, and five algal species. They were studied the extraction process and protein quality. This thesis also assessed the effects of each essential amino acid on myotube differentiation. This research was divided into three sections. In the first research section, the CDR was extracted by alkaline (sodium hydroxide; NaOH) and enzymatic (Alcalase and Flavourzyme) extractions. Extraction efficiencies were compared using protein recovery (%) and protein solubility (%). The Plackett-Burman experimental design screened factors for influent extraction efficiencies: solid-liquid ratio (SL ratio), enzyme per substrate (E/S), extraction time, pH, and temperature. The factors significantly influencing the extraction by Flavourzyme were SL ratio, E/S, and extraction time (p < 0.05). The predicted protein recovery from the extraction by Flavouryzme was the highest at 15.03%. The extraction by Alcalase by optimized pH and temperature provided the highest at 30.04% of predicted protein recovery in the same condition using Flavouryzme. In an extraction by 0.1 N NaOH, the predicted protein recovery was the highest at 36.42%. Increments in NaOH concentration and temperature influenced a higher protein yield but lower protein content. In solubility comparison, the protein extracted by enzymes could completely dissolve (100%), while the protein extracted by 0.1 N NaOH was low soluble (14.50%). The proteins extracted by higher alkaline concentration (1 N NaOH) and temperature were more solubilized (maximum at 94.78%). In comparing all extraction methods, the CDR protein extracted by Alcalase was the most effective because of the high protein recovery and completely solubility. The second section was the protein extraction from five different algal species: Arthrospira platensis, Cladophora glomerata, Porphyra tenera, Laminaria japonica, and Undaria pinnatifida, using the ultrasound-assisted alkaline extraction (UAAE). This method had a higher protein yield than conventional alkaline extraction. The protein extracted from A. platensis using 60% amplitude for 30 min was the highest yield at 81.86%. The digestibility of most algal proteins was close to that of standard soy and whey proteins (75.55-78.5%). The protein extracted from C. glomerata showed the highest protein digestibility (94.09%). Most algal proteins contained a high content of essential amino acids (EAAs), such as branch-chain amino acid, lysine, phenylalanine, and histidine, which meet body requirements. Although L. japonica protein had low levels of yield, EAAs constituent, and digestibility, it contained a high proportion of amino acids of umami taste (60.6%). Other components of algal proteins were found to have low contents of nucleic acids (0-8.57 mg/g) and carbohydrates (3.87-44.83 mg/g) but contained high phenolic content (6.13-48.67 mg/g). Therefore, algal proteins could be an alternative protein source appropriate for vegans and vegetarians. The last section evaluated the effects of each EAAs on myotube differentiation. The twelve mixtures containing different EAAs were formulated by the Plackett-Burman design. The result showed that only leucine affecting diameter, nuclear fusion index (NFI), and numbers of myotubes, which were significantly different at 90, 85, and 95% of the confidence interval, respectively. Even if leucine clearly affected myotube differentiation, other EAAs were still indispensable to myotube for its constituents, which were seen from a lower confidence interval than 95% of the diameter and NFI. Consequently, the protein mixture from CDR and algae could be a choice for vegan consumption to receive complete EAAs for muscle requirements.