Corn Stalk Pretreatment With Amino Acid Ionic Liquids(AAILs) And Effect Of Residual Aails On Tomato Growth

Corn straw contains a large number of refractory substances such as lignin and hemicellulose,which are difficult to achieve efficient utilization.Therefore,pretreatment is usually required before degradation.Based on the disadvantages of traditional ionic liquids,such as strong toxicity,poor biodegradability and difficult in utilizing the residual liquid,which cause secondary pollution to the environment.Therefore,a new type of amino acid ionic liquids,choline proline salt（[Ch][Pro]）,with high safety and environmental friendliness,was selected to pretreat corn straw.The pretreatment conditions were studied by single factor experiment and response surface analysis.The effects of[Ch][Pro]on the structure and composition of corn straw were studied by infrared spectroscopy and component analysis.Cellulase was used to hydrolyze corn straw before and after pretreatment to verify the pretreatment effect of[Ch][Pro].The toxicity of[Ch][Pro]residue on microorganisms and its effect on tomato growth under pot experiment conditions were further studied.The main experimental results are as follows:The optimum reaction conditions were selected by single factor experiments.On the basis of this,the Box-Behnken method was used to optimize the reaction conditions in the pretreatment process.The optimum pretreatment conditions for corn straw were 92℃,1.5 h and 1:13 solid-liquid ratio.The maximum lignin extraction rate predicted by the model was32.55%.The experimental results are very close to the predicted values of the model,which shows that the results are effective.The results of infrared spectroscopy showed that[Ch][Pro]caused some damage to the complex structure of corn stalk.The wavelength of 1600 cm^-1 represented the characteristic absorption peak of lignin,and all the characteristic almost peaks disappeared here,which indicated that[Ch][Pro]had a remarkable effect on lignin degradation.The intensity of the stretching vibration peak at the wavelength 1720-1744 cm^-1 decreased,which indicated that[Ch][Pro]could remove lignin or hemicellulose in the straw to varying degrees.The result of component analysis showed that[Ch][Pro]treatment could reduce the lignin content in straw and resuce the crystallinity of cellulose to increase the total sugar content.After enzymatic hydrolysis of the straw before and after pretreatment for 48 hours,it was found that the enzymatic hydrolysis rate of pretreated straw could reach 64.89%,which was 2.98 times higher than that before pretreatment.From the study on the growth of microorganisms in the treatment residue,it was found that Bacillus polymyxa could grow normally on the LB plate after mixing with the treatment residue of 150 mg·kg^-1,and the colony characteristics were obvious.The results showed that the treatment residue of different concentrations had different effects on the growth of tomato plants.The plant height,stem diameter,fresh weight,dry weight,root antioxidant enzyme activity and soil enzyme activity of tomatoes treated with residual liquid increased to different degrees.The treatment effect was the best when the residual liquid concentration was50 mg·kg^-1.The plant height,stem diameter and fresh weight of tomatoes were increased by44.02%,34.05%and 82.77%respectively,the total chlorophyll content was increased by37.10%,and the activities of SOD,POD and CAT in roots were increased by 60.04%,125.56%and 123.28%respectively.The activity of SOD in roots reached 81.18 U·g FW^-1 in60 days,which was 1.51 times higher than that in 30 days,and the content of MDA decreased by 26.69%.The urease,catalase and invertase in soil increased by 66.67%,92.00%and64.29%respectively,compared with the control.The urease activity in soil reached1.49 mg·g^-1·d^-1 in 60 days,which was 4.97 times higher than that in 30 days.The number of bacteria and actinomycetes increased and the number of fungi decreased in tomato rhizosphere soil,which gradually changed the soil type from fungal type to bacterial type.It is concluded that the application of residual liquid can effectively promote plant growth,improve photosynthesis and antioxidant capacity of plants,improve soil microenvironment and enhance soil fertility.It can be used as a potential fertilizer resource in production.