Structural properties of beds packed with agro-industrial solid by-products applicable for solid-state fermentation: Experimental data and effects on process performance

• Paper addressed structural properties of beds packed with agro-industrial wastes.
• Moisture content and packing technique markedly affected bed density and porosity.
• Sugar cane bagasse increases porosity of beds packed with milled material and bran.
• It was discussed how bed porosities influence on packed-bed bioreactor performance.
• Results are useful for heat and mass transfer modeling and simulation in reactors.

The knowledge of structural properties of beds packed with particles from agro-industrial solid wastes is important for modeling and simulation of heat and mass transfer in solid-state fermentation (SSF) in packed-bed bioreactors. This paper addresses the experimental determination of particle and bulk densities (ρpart and ρbulk) and porosities (ε) of beds packed with sugar cane bagasse (SCB), wheat bran (WB) and orange pulp and peel (OPP) and with mixtures of them. The effects of moisture content (MC) and packing technique on structural properties were evaluated. Microscopic analysis of cell-size was performed and the porosity along the fermentation was determined, as well as the endoglucanase yields for different proportions of a medium composed by SCB/WB. Results showed that MC affects significantly ρpart, ρbulk and ε. For OPP and WB, ε ranged from 0.4 to 0.7, depending on MC, and for SCB from 0.7 to 0.9, depending on MC and packing technique. For the composed media SCB:OPP:WB (1:2:2, weight) and SCB:WB (7:3), ε values were similar to the ones obtained for SCB. The growth of the fungi Myceliophthora thermophila I-1D3b and Trichoderma reesei QM9414 did not affect ε of the medium composed by SCB:WB. A comprehensive discussion on how the structural properties of solid matrices affect the performance of SSF processes was done, considering both operational aspects and bioproducts yields.

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