BIOPROSPECTING FOR AMYLOLYTIC ENZYME SECRETED BY FUNGI USING MICROALGAL BIOMASS AS A HYDROLYZABLE SUBSTRATE

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

Buenos Aires

Congreso; Congreso Conjunto SAIB-SAMIGE 2020; 2020

Sociedad Argentina de Investigación Bioquímica y Biología Molecular y(SAIB) y Asociación Civil de Microbiología General (SAMIGE)

Global warming associated with fossil fuels leads the exploration of alternative sources of energy, such as biofuels.Microalgae can be considered as an alternative feedstock for the production of bioethanol given its high photosyntheticefficiency and productivity, as well as the independence of fertile lands. Biomass saccharification represents the mainchallenge for economic and environmental feasible production of ethanol from biomass. One of the challenges to makeethanol production cost-effective is to explore economic and practical alternatives for totally or partially replacement of thecurrent biomass pretreatment processes of physico-chemical hydrolysis, which requires a large amount of energy andgenerates polluting waste. Conversely, enzymatic hydrolysis methods are selective, simpler to operate, and lower energy-intensive consumption. A promising option is the search for microorganisms, especially fungi secreting hydrolytic enzymescapable of efficiently degrading the starch molecules contained in the microalgal biomass. Thus, the purpose of this studywas to search for mixtures of hydrolytic enzymes from fungi capable of efficiently saccharified algal biomass as a source ofnon-expensive sugars.In this work, we isolated 31 fungal strains isolated from environmental samples were screened and cultured in liquid mediumor solid substrate, both based on wheat bran. For the tests, induced biomass of Chlamydomonas reinhardtii and Chlorellasorokiniana with high carbohydrate content (45 and 55% of their dry weight respectively) was used. The enzymatic reactionswere carried out taking every 24 h and during 5-8 days the supernatant of the growth culture medium of each fungal strainwith 1% microalgal biomass w/v, at pH 5, 55ºC for 1 h. Enzyme activity was measured in Units (U), where one unit wasdefined as the amount of enzyme necessary to generate 1 mMol of product /min. The four most promising strains belong tothe genera Aspergillus, Alternaria, Trichoderma and Penicillium. When induced using liquid medium, these strains releasedalgal saccharifying enzymes at maximum activities of 483, 20, 246 and 297 mU/ mL respectively, when induced onto solidwheat brand, the same strains produced maximum saccharifying activities at of 3,660; 1,070; 2,225; or 1,493 mU/mL at 8days of induction,respectively.The production yields of enzymes / g of bran for Aspergillus, Trichoderma and Penicillium were 29, 18 and 12 U / g of branrespectively. The protein profiles of the enzyme supernatants were analyzed through SDS gels and by using native-polyacrilamyde gels. Multiple bands for amylolytic activities were observed for each of the strains, additionally showingspecific time-course of induction. This study uncovers an interesting diversity of amylolytic enzymes, which will become astarting point for current research on protein identification and optimization of algal biomass saccharification and conversioninto bioethanol.