Centre of Biological Engineering of the University of Minho

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Comparison of different pretreatment processes envisaging the potential use of food waste as microalgae substrate

Publication . Marques, Fabiana; Pereira, Francisco; Machado, Luís; Martins, Joana T.; Pereira, Ricardo N.; Costa, Monya; Genisheva, Zlatina; Pereira, Hugo; Vicente, António A.; Teixeira, José A.; Geada, Pedro

A significant fraction of the food produced worldwide is currently lost or wasted throughout the supply chain, squandering natural and economic resources. Food waste valorization will be an important necessity in the coming years. This work investigates the ability of food waste to serve as a viable nutritional substrate for the heterotrophic growth of Chlorella vulgaris. The impact of different pretreatments on the elemental composition and microbial contamination of seven retail food waste mixtures was evaluated. Among the pretreatment methods applied to the food waste formulations, autoclaving was able to eliminate all microbial contamination and increase the availability of reducing sugars by 30%. Ohmic heating was also able to eliminate most of the contaminations in the food wastes in shorter time periods than autoclave. However, it has reduced the availability of reducing sugars, making it less preferable for microalgae heterotrophic cultivation. The direct utilization of food waste containing essential nutrients from fruits, vegetables, dairy and bakery products, and meat on the heterotrophic growth of microalgae allowed a biomass concentration of 2.2 x 108 cells center dot mL-1, being the culture able to consume more than 42% of the reducing sugars present in the substrate, thus demonstrating the economic and environmental potential of these wastes.

2024-04Journal article

Open access

Influence of different processing techniques on microalgal protein extraction

Publication . Moreira, Catarina; Ferreira-Santos, Pedro; Nunes, Rafaela; Carvalho, Bernardo; Pereira, Hugo; Teixeira, José A.; Rocha, Cristina M.R.

The nutrient-rich composition of microalgae biomass positions it as a highly promising natural food ingredient. This holds the potential to not only enhance the nutritional value of various food products but also simultaneously alter their structural attributes.This work investigated the effect of five protein extraction techniques such as freeze-thawing, enzymatic-assisted extraction, high-pressure homogenization, ultrasounds-assisted extraction, and pH adjustment (pH 7, pH 10, and pH 13) in protein yield, and subsequente cell and protein structure of three microalgal suspensions, namely, Chlorella vulgaris, Nannochloropsis oceanica, and Tetraselmis chui. In Chlorella vulgaris, freeze- thawing and high-pressure homogenization exhibited a higher effect in terms of protein yield (similar to 26.60 g (protein) /100 g (protein microalgae)). The same occurred for Nannochloropsis oceanica with also ultrasounds-assisted extractions and pH 7 and 10 having a protein yield above 30 %. Tetraselmis chui was similar to Chlorella vulgaris (>20.00 g (protein) /100 g (protein microalgae)) for freeze-thawing, high-pressure homogenization and ultrasound-assisted extraction. Enzymatic-assisted had a the lower protein yield for all the three microalgae (<10.00 g (protein) /100 g (protein microalgae)). The majority of proteins extracted from Chlorella vulgaris samples had molecular weights exceeding 337 kDa, whereas proteins extracted from Nannochloropsis and Tetraselmis had molecular weights ranging from 5 to 50 kDa. alpha-helices occurred in proteins extracted from Chlorella vulgaris through freeze-thawing and enzymatic-assisted extraction, while Nannochloropsis and Tetraselmis only had beta-sheet. In conclusion, for optimal protein yield recovery, methodologies such as freeze-thawing and high-pressure homogenization are the most efficient across all studied microalgae. The method selected for extraction had a greater impact on both the protein yield and structure for spray-dried cells.

2025-03Journal article

Open access