BIOPROSPECTING OF FUNGAL ENZYMES FOR APPLICATION IN MICROALGAL BIOMASS BIOREFINERIES

BADER, ARACELI N.; SÁNCHEZ RIZZA, LARA; CONSOLO, VERÓNICA FABIANA; CURATTI, LEONARDO

Los Cocos, Córdoba

Congreso; XVIII Congreso Argentino de Microbiología General SAMIGE 2022.; 2022

Sociedad Argentina de Microbiología General, SAMIGE

Microalgae biomass is a promising feedstock for biofuels, feed/food and biomaterials. However, their production and commercialization as a single product obtained from these microorganisms is not yet economically viable. The most promising alternative proposes obtaining multiple products from a biomass biorefinery, although this process faces several techno-economic challenges. The aim of this study was to identify a suitable source of hydrolytic enzymes for the saccharification of microalgae biomass. Twenty-six fungal isolates were screened for their ability to produce extracellular hydrolytic enzymes able to release sugars from Chlamydomonas reinhardtii biomass. Thus, Aspergillus niger IB-34 strain resulted as a candidate strain. Solid-state fermentation using wheat bran produced the most active enzyme preparations. A proteomic approach by LC-MS identified sixty-five proteins, most of which corresponded to predicted secreted proteins belonging to the gene ontology categories of catalytic activity and hydrolase activity of glycosyl and O-glycosyl compounds. Defatted biomass of two relevant algal strains for the production of commodities, such as Chlorella sorokiniana and Scenedesmus obliquus, were completely saccharified at a high biomass load of 10% (w/v), after a mild pretreatment at 80 °C for 10 min. Defatted and saccharified biomass of both strains was subsequently converted into ethanol by fermentation with Saccharomyces cerevisiae at maximum theoretical efficiency, either by separate or simultaneous saccharification and fermentation. Insoluble protein remaining after the biomass was defatted with organic solvent and enzymatically saccharified was found to have a high digestibility in an in vitro digestion test. Proof-of-concept is presented for an enzyme-assisted biomass biorefinery, which recovered 81% of the main biomass fractions in a likely active form for the conversion of lipids and carbohydrates into biofuels and proteins into feed/food.