Protein and carbohydrate extraction from S. platensis biomass by ultrasound and mechanical agitation

Spirulina platensis is considered an alternative and excellent source of protein [46-63% dry basis (DB)], having protein levels comparable to meat and soybeans. Thus, it can be considered an adequate ingredient to supply the necessity of this compound in the food industry. Its carbohydrates (8-14% DB) may also be a useful food ingredient or a potential source of bioenergy. Thus, extracting these compounds from the microalgae biomass will maximize its exploitation. Sonication can completely or partially degrade the microalgal cell wall, providing a useful technique to extract the protein and carbohydrate. This study used a sequential strategy of experimental design (fractional factorial design and central composite rotatable design) to evaluate the protein and carbohydrate extraction from S. platensis defatted biomass using ultrasonic waves and mechanical agitation, under alkaline conditions. The optimal conditions for protein and carbohydrate co-extraction were established by selecting and maximizing the variables that significantly influenced the extraction. The optimized percentages recovery from the extraction process yielded 75.76% protein and 41.52% carbohydrate at 33-40min sonication and 40-55min agitation. The protein fraction may be further concentrated and purified for use in food formulations, and the carbohydrates may be a useful feedstock for bioethanol production.