Combined Remediation and Protein Production Using Microalgae Growth on Waste Bakery Products

A new concept of bakery industry waste use as a nutrient source for the production of proteins by microalgae growth has been developed. The proposed ideas provide an innovative approach to establish a system to valorise bakery industry waste, more specifically, the so-called waste ´biscuits flour´, and to produce rich protein algal biomass, which could potentially be applied in feed industry. Biscuits flour was used as carbon and nutrients source in mixotrophic growth of Chlorella sorokiniana , pure culture, and a mixed culture of microalgae taken from a natural environment. The feasibility of utilizing bakery waste, raw and hydrolysate, for algal biomass production was investigated and compared with the growth of the microalgae in WARIS-H medium and in natural water. Although better biomass growth is achieved with hydrolysed flour, highest concentration of proteins were obtained for C. sorokiniana and the mixed culture, 34.63 and 24.06% respectively, when the waste flour is not hydrolised at the beginning of the assay. These figures contrast with the lower protein content in both cultures, 3.63 and 8.94%, respectively, when WARIS-H medium and natural water are used as nutrient sources. These good preliminary results, together with a situation in which the supply of raw materials for livestock and farmed fish is beginning to become critical, give rich-protein microalgae production increasing relevance as a source of feed. Graphical Abstract