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Development of novel microalgal mutants with improved pigmentation and protein contents for industrial waste-based fermentation
Publication . Santos, Mafalda Trovão dos; Freitas, Maria Filomena; Silva, Joana; Pereira, Hugo
Microalgae are a promising alternative feedstock to achieve the second goal of the 2030 Agenda established by the United Nations: to end hunger, achieve food security and improved nutrition and promote sustainable agriculture. However, microalgal production and commercialisation still face several hurdles, namely the high production costs and the unappealing sensory properties of the biomass.
To overcome the abovementioned limitations, improved strains of Chlorella vulgaris and Scenedesmus rubescens were generated by chemical random mutagenesis. At this stage, two novel selection methods were developed: one to select chlorophyll-deficient mutants with a novel metabolic inhibitor, oxyfluorfen, which led to the selection of a yellow and a white mutant of C. vulgaris and a brownish mutant of S. rubescens; and another using fluorescence-activated cell sorting to select protein-rich mutants, that allowed to select a green mutant of C. vulgaris, 8GF4. Additionally, nicotine was also used to select a yellow mutant (7Y) of C. vulgaris and an orange mutant of S. rubescens for food and feed applications.
From the mutants generated, mutant 8GF4 displayed higher biomass and protein productivity, and was further validated as a biostimulant for agricultural applications, improving the germination of garden cress seeds. Moreover, a novel optimisation pipeline was developed to optimise the latter and a yellow (7Y) and white (31W) C. vulgaris mutants. This methodology allowed to improve the biomass productivity, colour, and protein content and productivity by up to 70, 20, 61 and 94%, respectively. Finally, a waste-based medium was formulated to cultivate mutant 7Y, reaching a biomass productivity of 22 g L-1 d-1 at industrial scale.
Overall, this study optimised the whole production pipeline, from strain improvement to bioprocess optimisation and validation of cultivation under a waste-based medium, to overcome the challenges of the biobased industry, allowing to improve the attractiveness, cost-effectiveness and nutritional profiles of microalgal products.
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Fundação para a Ciência e a Tecnologia
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2020.06814.BD