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Characterization and Integrated Process of Pretreatment and Enzymatic Hydrolysis of Corn Straw

Serafín Muñoz, Alma Hortensia, Molina Guerrero, Carlos Eduardo, Gutierrez Ortega, Norma Leticia, Leal Vaca, Julio Cesar, Alvarez Vargas, Aurelio, Cano Canchola, Carmen
Waste and biomass valorization 2019 v.10 no.7 pp. 1857-1871
Fourier transform infrared spectroscopy, Pleurotus, biomass, cellulose, chemical oxygen demand, corn straw, delignification, enzymatic hydrolysis, fungi, glucose, growing media, hemicellulose, hydrogen peroxide, lignin, liquids, pH, reducing sugars, scanning electron microscopy, water utilization, xylose
The chemical pretreatment of biomass has been integrated with enzyme production through the recycling of aqueous fractions. Alkaline/H₂O₂ delignification of corn straw (CS) was performed to obtain a 75.1% w/w cellulose solid fraction and to dissolve 93.4 and 83.5%, of the original lignin and hemicelluloses, respectively. Next, a Pleurotus cystidiosus native strain was left to grow for 120 h in the resulting liquid fraction. After filtering the cells, the liquid medium was used alone or combined with the commercial enzyme. To reduce chemical and water usage, the liquid fraction from pretreatment was recycled to perform another treatment; the pH, CS, and H₂O₂ were adjusted. A process integrated with P. cystidiosus was grown again and enzymatic hydrolysis was realized. Samples of every liquid fraction from the fungal growing medium were analyzed to determine the chemical oxygen demand (OCD), glucose (Glu), xylose (Xyl), and total reducing sugars (RS). Separately, to obtain valuable polymers from this integration process, solid hemicellulose and lignin were isolated from the remaining liquid fractions through pH variation. The composition of the samples was determined using scanning electron microscopy (SEM), optical stereoscopic microscopy and Fourier transform infrared spectroscopy (FT-IR) and was compared with commercial homologs. The maximum conversion of cellulose to glucose by the obtained liquid fraction of the fungal medium was 61.3 ± 0.9% of the theoretical conversion yield of the commercial enzyme. Similarly, the conversion of hemicelluloses to xylose was 69.5 ± 1.5%. Finally, in this work, an integrated platform for cellulose, hemicellulose, lignin, enzymatic extract and sugars production, which also significantly reduces water consumption, was proposed.