349 / 2018-07-31 22:47:49

Effect of microwave combined with P. chrysosporium pretreatment on enzymatic hydrolysis of distiller's grains biomass for fermentable sugars

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With the depletion of the fossil energy and the demand of the global energy, lignocellulosic biomass has become very important as a promising raw material for bioethanol. Distillers grains, mainly composed of cellulose and hemicellulose, is one of the most abundant food processing byproducts producing from white spirit brewage in China. Using distillers grains as the raw material to prepare the fermentable sugar for ethanol production, is not only beneficial to recycling of distillers grains, but also can promote the recycle development of traditional distillery. However, the pretreatment process of lignocellulose is a critical step in the production of fuel ethanol, due to the complexity and tightness of the lignocellulose structure. Therefore, it is of great significance to investigate the influence of different pretreatments on the enzymatic hydrolysis of distillers grains biomass for fermentable sugars. In this paper, the effects of combining for microwave and P. chrysosporium pretreatment on the yield of fermentable reducing sugar (YRS) were studied by the response surface methodology (RSM), and the optimum pretreatment conditions were determined. Morevoer, the changes of structural characteristics were studied by scanning electron microscopy (SEM), X-diffraction (XRD) and fourier-transform infrared spectrometry (FTIR). The optimal ultrasound pretreatment condition was identified as ultrasound power of 100 W, hydrolysis time of 3 min, and solid-liquid ratio of 1:10 (g/mL). Under this condition, the YRS was 19.74%. The combining pretreatment results showed that the combinations of P. chrysosporium led to a significant increase in YRS as compared with that from any single pretreatment. The YRS was reached up to 25.21% when combined microwave with P. chrysosporium. The SEM showed significant structural changes and the surface became increasingly coarse, the gaps between cellulose fibers were visible, and many pores were developed. Moreover, X-ray diffractometry and FTIR analysis revealed that the cellulose crystallinity of pretreated distillers grains was changed in different degrees, and the strength of characteristic peaks for corresponding typical functional groups of each component are changed compared with the feedstock. This suggests that the combination of microwave and P. chrysosporium pretreatment is effective in improving the enzymoysis efficiency of distillers grains.