| The northern region is one of the main agricultural planting production areas in China.However,due to the cold and dry climate and the sandy soil,the agricultural residues are decomposed slowly or even cannot be completely degraded,not only making it unable to be used as a fertilizer source in the current season,but also causing the phenomenon that straw and subsequent crops compete for nitrogen and enevtally affect the growth of crops.Stacked straws are burned in large quantities,which cause waste of resources and serious air pollution.Therefore,in order to improve the status of straw degradation in cold areas and make rational use of straw resources,research on low-temperature resistant cellulose-degrading strains is necessary.A strain was isolated from 10℃in this research,and the enzyme-producing fermentation conditions and cellulase characteristics of this strain were studied through single-factor experiments and RSM（Response surface method）.Also,the isolated strain was applied to the degradation of rice straw at low temperature（10℃）,the straw degradation ratio and cellulase activity in the fermentation processes were observed.In addition,in order to recycle straw resources,the diluted straw fermentation broth was used for the cultivation of rice seeds,and the effects of the fermentation broth on the growth of rice seedlings and germination rate of rice seeds under salt stress were observed.Through 18S molecular biology identification,the isolated strain was identified as Penicillium sp.and named Penicillium sp.Ji TF01.This strain had good genetic stability at low temperatures and could produce 90.35%of the maximum cellulase activity at 10℃.At the same time,after optimization of the fermentation conditions of strain by RSM,it was found that the maxium cellulase activity of 31.25 U/m L was obtained when the inoculation was 2.78%,the incubation time was 13.36 days and the p H was 6.67.In addition,the cellulase produced by the strain has good enzyme properties in the p H range of 2.00-7.00,temperature range of5-50℃,and salt stress of 1～5 mol/L.The integrated process of the acid pretreatment and acid fermentation at low temperature was processed.It was found that compared with the fermentation process under the optimized condition,the cellulase activity increased by 3.61 U/m L（p H 4.00）at 13 days of fermentation under the acid integrated process,and the straw degradation ratio increased by 7.08%（p H 3.00）at 25days of culture.In addition,it was found that the 10-5 and 10-6 diluted straw fermentation broth had the most obvious effect on the growth of rice seedlings;and after 3 days of culture with 10-6 diluted straw fermentation broth,the germenation rate of rice seeds under 100 and 200 mmol/L salt stress was increased signifiantly.Enzyme production and enzyme characteristics of the isolated low-temperature cellulose-degrading strain Ji TF01 were studied in this paper,and this strain was applied to degrade straw at low temperatures.Besides,the degraded straw fermentation broth was used for the cultivation of the rice seeds to observe the fermentation broth on the growth of plant.This research process provides the basic theoretical basis and technical parameters for the degradation and recycling of straw at low temperatures,and is of great significance to the disposal and resource utilization of straw in cold regions. |
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