| Acorn of Quercus L. species, a kind of wild plant resources which can be used as biomass material for fermentation, is renewable and aboundant. Acorn tannin can precipitate proteins and the features of inhibiting enzyme activity and the growth of microorganisms, greatly limits the application of Quercus L. species acorn. Therefore, we need to develop a new kind of acorn tannin extraction technology coupled with VHG fermentation of acorn starch, so as to realize comprehensive utilization of acorn resources and efficient conversion.In this study, acorn tannin extraction technology which used 40% ethanol-water solution was established. Under the conditions of 600 r/min, 3 h,60℃, solid-liquid ratio 1:20, total tannin removal rate of three times extraction is above 80%, the acorn tannin residual content determined by Folin-Denis method decreased from 7.4% to 1.5%. The influence of residual tannin content of three times extraction on a-amylase, glucoamylase activity were studied. The influence of residual tannin content of three times extraction on Pachysolen tannophilus (CICC1770) and Saccharomyces cerevisiae (H5) strain growth characteristics and ethanol production capacity were studied, too. Results show that, when the tannin content is more than 1.5%, tannin greatly inhibit the inhibition of bacterial growth and ethanol production capacity, a-amylase and glucoamylase relative activity reduced more than 10%; when the tannin content is less than 1%, the influence of tannin on the two kinds of strains growth and ethanol production capacity is very small, the relative enzyme activity of the two kinds enzymes are kept at more than 90%. Experiments were planned to add glycerol and tannase to reduce the impact of tannin inhibition starins.Further research on acorn starch VHG fermentation was studied. The acorn composition was measured, the acorn starch structure and pasting properties are studied. Then I compared the ethanol fermentation ability of acorn starch with corn and cassava starch so as to develop a novel kind of composite sacchariferous agent for acorn resources and optimize VHG fermentation parameters. Results show that the acorn starch structure and pasting properties were similar to corn starch, a new type of composite saccharifying agent (glucoamylase 250 U/g, amylase 20 U/g, xylanase 60 U/g, acid protease 50 U/g, cellulase 60 U/g, hemicellulase 20 U/g, tannase 0.2 U/g) was developed for acorn resources, Under the conditions of optimized VHG fermentation (solid-liquid ratio 1:2.4,10% inoculation quantity,84 h, M3013 strain,32℃), ethanol production detected by high performance liquid chromatography (HPLC) increased from 66.3 g/L to 89 g/L, increased by 34.2%; The utilization rate of acorn starch increased from 64.8% to 87.1%.In the last part of this work, the process simulation model of acorn tannin extraction and acorn starch VHG fermentation with the capacity of 240 t/d acorn was developed based on the Aspen Plus. The mass balance and energy balance of this process were calculated. Results show that the capacity of 240 t/d acorn required 14.77 t/h fresh water and 24.65 t/h waste water, produced 3.63 t/h ethanol. The capacity of 240t/d acorn required energy input is 91.25×109 J/h. The process simulation results(material consumption, water consumption, energy consumption) of acorn tannin extraction coupled with acorn starch VHG fermentation provided the reference for process selection and economic evaluation. |
