Phanerochaete chrysosporium treatment is less effective as a biological pretreatment on feedstock with larger particle sizes. We hypothesized that the improved effectiveness of the pretreatment when smaller particle sizes are used may be due to the inherently higher bulk density with smaller particle sizes. The effects of substrate bulk density and particle size on the efficacy of P. chrysosporium pretreatment of switchgrass (Panicum virgatum) was tested experimentally. Phanerochaete chrysosporium was grown on senesced switchgrass (2 different particle sizes) with various bulk densities. In all treatments, the fungal-pretreated samples released more glucose during enzymatic saccharification than the control sample. Substrate bulk density was a statistically significant factor in explaining the variation in the amount of glucose released per gram of substrate used. However, the particle size was not found to be a significant factor. On-farm switchgrass pretreatment may not require particle size reduction if the switchgrass is supplied in high-density bales.
Pretreatment is considered a necessary step in the use of lignocellulosic biomass for biochemical conversion to higher value products. There are multiple choices of chemicals for pretreatment in industrial settings, however on-farm choices are constrained to those that function well at near ambient conditions with minimal specialized equipment, personnel training, and require limited waste disposal. This work presents a novel pretreatment system biomass using a recirculating, saturated calcium hydroxide (lime) solution in an up-flow, high solids (14-16% w/w) configuration at ambient conditions. In this system, lime solids were efficiently consumed, post-pretreatment washing of substrate was not required, and energy and resources were conserved. Pretreatment effectiveness was assessed by glucose yield comparisons for both switchgrass and corn stover. Based on mean glucose yields from 5 mm corn stover, lime pretreatment would require 350 kg of dry stover to produce 100 kg glucose at a chemical cost of $8.67 while NaOH pretreatment would require 300 kg of chemical at a cost of $22.38.
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