Screening Of High-efficiency Cellulolytic Bacteria And Its Degradation Effect On Returning Straw

In order to improve the tobacco-growing soil and promote the promotion of straw returning to the tobacco area,it is an effective solution to seek cellulose decomposing bacteria that promote the efficient decomposition of straw.In this study,tobacco-planting soils in different tobacco areas in Guizhou were used as materials for screening cellulolytic bacteria,flue-cured tobacco straws and corn stalks were used as carbon sources to screen cellulolytic bacteria,and compound inoculants were prepared to obtain high-efficiency degradation of straw cellulose.Strains or compound inoculants.The cellulose decomposing bacteria and compound inoculants were screened through indoor culture and pot experiments to explore the degradation effect of the sieved cellulosic bacteria and compound inoculants,the best form of straw returning to the field and its effects on the physical and chemical properties of tobacco-growing soil and the main chemical properties of tobacco leaves.The research results were summarized as follows:（1）Using tobacco-growing soil such as Zunyi,Anshun and Bijie in Guizhou as materials,corn stalks and flue-cured tobacco residues are the only carbon sources to screen cellulolytic bacteria.D/d is greater than 2.5,6 strains with strong cellulose decomposing ability,of which 3 strains such as FCM-1,FCM-10,FCM-11 are from Meitan tobacco area in Zunyi,FTZ-5 is from Leshan tobacco area in Zunyi,FCY-2 From Anshun Yangwu Tobacco District,FCW-2 from Bijie Weining Tobacco District,FCM-10 has a D/d of 4.2.FTZ-5 was screened using flue-cured tobacco residues as a carbon source,and FCM-1,FCM-10,FCM-11,FCY-2,and FCW-2 were screened using corn stover as a carbon source.They were screened by morphology,16S r DNA sequence and Phylogenetic analysis showed that the strains using corn stover as a carbon source belonged to Cellulosimicrobium,and the strains using flue-cured tobacco residue as a carbon source belonged to Streptomyces.（2）Through the strain antagonism test,the 6 strains did not have antagonism when paired with each other;through the growth curve determination,the 6 strains were in the logarithmic growth 16 h～44 h.（3）The Caboxy Methyl Cellulose enzymes activity test showed that the enzyme activity of the composite bacteria was higher than that of the single bacteria.Among them,the"FCY-2+FTZ-5"composite bacteria had the highest enzyme activity.At the 6th day,the CMCase activity reached 517.37 U/m L.In addition,although the Cellulosae strains have similar morphological characteristics,there are differences in cellulase activity.The maximum enzyme activity of the FCM-10 strain on the 7th day is 260.45 U/m L,and the cellulase strains are compounded with The maximum enzyme activity of"FCM-1+FCM-10"treatment was358.11 U/m L on the 7th day,and the cellulase activity of the composite bacterial agent was higher than that of the single bacterial agent;the enzyme activity of the FTZ strain reached the maximum of 321.23 U/m L on the 2nd day.In order to achieve the goal of degrading both corn stalks and flue-cured tobacco residues,the"FCY-2+FTZ-5"compound inoculum selected with corn and flue-cured tobacco stalks as carbon sources is the best combined inoculum.（4）The enzyme solution of FCM-10,FCY-2,FTZ-5 and their combination of 3 kinds of complex inoculants was inoculated into corn stalks at a 5%inoculum amount.The results showed that adding cellulose decomposing inoculants can be Effectively promote the degradation of straw,the compound inoculum is better than the single strain,and the effect is best when the inoculant is added for 50 days.The maximum weight loss rate of corn stalks treated with"FCY-2+FTZ-5"was 76.53%,followed by"FCM-10+FTZ-5"and"FCM-10+FCY-2",and the weight loss rates were 73.60%and 67.77%,respectively.The weight loss rate of flue-cured tobacco residue is"FCM-10+FCY-2","FCY-2+FTZ-5",and"FCM-10+FTZ-5",and the weight loss rates are 74.49%,74.32%and 73.95%,respectively.The degradation rate of corn stalk hemicellulose,cellulose and lignin is higher than that of flue-cured tobacco residue,and the degradation rate of composite inoculum is higher than that of single inoculum treatment.The most conducive to the degradation of corn stover hemicellulose,cellulose,and lignin is"FCY-2+FTZ-5",and the most conducive to flue-cured tobacco residue.The inoculum that degrades hemicellulose,cellulose and lignin is"FCM-10+FTZ-5".（5）The degradation products of straw after treatment with different inoculants were at3400 cm^-1,2930～2920 cm^-1,1630～1640 cm^-1,1520～1500 cm^-1,1420 cm^-1,1250 cm^-1and1100～1000 cm^-1.The intensity of one absorption peak decreased,and the difference between the intensity of the absorption peak without straw in the wavenumber interval of 1000～1640cm^-1was the largest.After corn stalks were treated with inoculants,the relative intensity of absorption peaks at 3400,1640,and 1310 cm^-1decreased,while the relative intensity of flue-cured tobacco waste decreased significantly at 3400,2925 cm^-1peaks,indicating aliphatic compounds and lignin,Part of the benzene ring,lignocellulose,cellulose,hemicellulose or polysaccharide content has been degraded.From the perspective of degradation products,the"FCY-2+FTZ-5"combination is the best.（6）The degradation rate of 80 cm,10～15 cm,3～5 cm and powdered corn stalks under the treatment of adding"FCY-2+FTZ-5"compound inoculant was 48.28%,56.38%,63.94%,73.33%,respectively,Which are 21.37%,26.97%,33.51%and 13.33%higher than those without bacterial fertilizer.Although the powder form has the best degradation effect,considering the high labor input and processing cost,the corn stalks of 3～5cm form are more conducive to returning to the field.（7）The pot experiment showed that compared with no inoculation,corn stalks treated with inoculants were easier to degrade,and the degradation rates of straws treated with different inoculants were different.Corn stalks treated with FCM-10 and FCY-2 strains.The degradation rate was the highest,79.98%and 78.41%respectively,which were 1.15 and 1.18times that of the control.Straw returning to the field can effectively reduce soil bulk density,increase soil porosity,and promote the formation of aggregates.Among them,FCY-2 and FCM-10 treatments have the smallest soil bulk density,which are 1.20g/cm3 and 1.24g/cm3,respectively,which are the control.0.92,0.95 times;the soil porosity of adding FCY-2inoculum was the largest,54.51%;FCY-2 and FCM-10 inoculum treatment also increased>2mm and 2～0.25 mm particle size.The mass fraction of aggregates promotes the formation of large soil aggregates.There are significant differences in the conversion of organic matter in the soil under different inoculum treatments.The degradation of organic matter in the soil treated with FCY-2 inoculant is the fastest,which is 1.09 times that of no inoculant;the addition of inoculants to the field improves soil nitrogen in the mass stage Effectiveness,the total nitrogen content of corn stover treated with FCY-2 inoculum increased the most significantly.Under the condition of returning straw to the field,the tobacco plants of each treatment grew well,and the agronomic traits were all within the normal range.The growth of FCM-1 tobacco plants was better than other treatments;the total nitrogen and available potassium content of the tobacco leaves at the cluster stage,the blooming stage and the budding stage showed In order to decrease first and then increase,FCM-10 is most conducive to the decrease of nitrogen content and the increase of potassium in tobacco leaves at the budding stage.In summary,for flue-cured tobacco production,FCM-10 and FCY-2 are the best high-efficiency cellulose degrading bacteria in Guizhou tobacco areas.