Induced production of amylolytic cazymes of a native Aspergillus niger strain using wheat bran and microalgal biomass as a hydrolyzable substrate

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

Encuentro virtual

Congreso; Reunión conjunta SAIB-SAMIGE 2021; 2021

SAIB-SAMIGE

INDUCED PRODUCTION OF AMYLOLYTIC CAZYMES OF A NATIVE Aspergillus niger STRAIN USING WHEAT BRAN AND MICROALGAL BIOMASS AS A HYDROLYZABLE SUBSTRATEBader AN, Sánchez Rizza L, Consolo VF, Curatti LInstituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC-CONICET) y Fundación para Investigaciones Biológicas Aplicadas (FIBA).E-mail: aracelibdr@gmail.comMicroalgae can be considered as a source for the production of bioethanol given its great photosynthetic efficiency and productivity as well as the independence of fertile lands as an alternative energy source to fossil fuels. One of the challenges to maximize bioethanol production is to explore economic and practical alternatives to totally or partially replace the current biomass pretreatment processes such as physical-chemical hydrolysis, a process that, in addition to requiring a large amount of energy and generating polluting waste it can lead to the breakdown of fermentable sugars. Enzymatic hydrolysis methods are selective, simple to operate, and low in energy consumption, although they have a high cost. A promising option is the search for fungal secreting hydrolytic enzymes capable of efficiently degrading the starch molecules contained in the microalgal biomass. The aim of this study was to characterize the enzymatic secretion profiling from a native fungal strain of Aspergillus niger and optimize the enzymatic hydrolysis conditions against different microalgal biomasses. For fungal enzymatic induction, the native fungal strain IB-34 was grown in glucose potato agar medium at 25 °C for 7 d until sporulation. A suspension of 1 x 106 conidia/ml was prepared to inoculate solid substrate based on wheat bran and biomass from the microalgae Scenedesmus obliquus and Chlorella sorokiniana. Cultures were incubated for 8 d and then the extraction of the enzymes was performed using NaAc buffer solution at pH 5. Determination of enzymatic activity after induction on C. sorokiniana biomass reached 1389 ± 323 U / L, for wheat bran 1758 ± 360 and 1085 ± 553 for S. obliquus respectively. The protein profiles of each enzyme extracts were characterized in SDS-PAGE gels and in all samples amylolytic activity was strongly visualized by zymography using starch as substrate. Enzymatic saccharification tests were carried out on biomass of C. reinhardtii, C. sorokiniana and S. obliquus at 20% solid load for 24 h, reaching ​​ 53, 34 and 18 g / L of reducing sugars and hydrolysis efficiency of 60, 30 and 18% respectively. To identify the extracellular enzymes involved in the degradation of wheat bran medium the secretome of the culture supernatant of the fungus were analyzed by MS-MS mass spectrometry. As expected it was found that the fungus secreted mainly alpha amylase and glucoamylase enzymes although other as cellobiohydrolases and xylanases were determined. These results suggest that the A. niger strain IB-34 is a good candidate for the saccharification and biorefinery of microalgae biomass, to achieve a more profitable biofuel production, using the concepts of circular economy.