Solid-liquid extraction of cellulases from fungal solid-state cultivation in a packed bed bioreactor
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pISSN: 0256-1115 eISSN: 1975-7220
INVITED REVIEW PAPER
INVITED REVIEW PAPER
Solid-liquid extraction of cellulases from fungal solid-state cultivation in a packed bed bioreactor Samuel Pratavieira de Oliveira*, Natalia Alvarez Rodrigues*, Priscila Aparecida Casciatori-Frassatto**, and Fernanda Perpétua Casciatori*,† *Department of Chemical Engineering, Federal University of São Carlos (UFSCar), Rodovia Washington Luiz km 235 (SP 310), 13565-905, São Carlos - SP, Brazil **Department of Chemistry and Environmental Sciences, Institute of Biosciences, Letters and Exact Sciences, São Paulo State University (UNESP), Cristóvão Colombo 2265, 15054-000, São José do Rio Preto - SP, Brazil (Received 26 February 2020 • Revised 8 May 2020 • Accepted 13 May 2020) AbstractCellulases are enzymes required for the production of second-generation ethanol (E2G) via biochemical route. The current paper reports the development of an apparatus for solid-liquid extraction of cellulases from solidstate fermentation (SSF) carried out in a packed bed bioreactor (PBB), operated as batch and as semicontinuous. The case study was the cultivation of Myceliophthora thermophila I-1D3b on sugarcane bagasse (SCB) and wheat bran (WB) (7 : 3 w/w). The current work integrates the PBB to the first downstream step for recovering the enzymes produced by SSF. The substrate was inoculated and packed into the modules that composed the PBB. The fermentation occurred at 45 oC and air was supplied with flow rate of 350 L/h. At the end of the cultivations, each module was placed in an extraction column, a dynamic closed system in which distilled water was circulated and made to percolate the cultivated material. Variables tested were volume of water per mass of substrate, water flow rate and time of percolation. Higher contact time (120 min) and higher flow rate (2.4 m³/h) allowed us to recover up to 85% of total enzyme activity by percolation. Lower volume (20 mL/g) provides higher titer extract. The apparatus showed to be promising for SSF downstream, mainly for semicontinuous operation of PPBs. Keywords: Fixed Bed, Downstream, Cellulolytic Enzymes, Bioethanol, Biorefineries
ising alternative biotechnological process to produce enzymes required by E2G biochemical route, mainly cellulases. Additionally, SSF can be performed with different combinations of substrates, microorganisms and operational conditions. Besides cellulases, other high-added value biomolecules can be obtained. Therefore, biorefineries can explore such biomolecules for self-supply (enzymes and organic acids, for instance) or for commercialization (pigments, gums, biosurfactants, nanocellulose, and others). Moreover, byproducts of the biorefinery can be used as substrates [3,6]. SSF may be defined as the growth of microorganisms on wet solid particles [7]. Due to the lower water activity in SSF systems in comparison to traditional submerged fermentation (SmF), the microorganisms that most adapt to SSF are filamentous fungi. Among them, thermophilic fungi stand out for producing thermostabl
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