四川中烟工业有限责任公司

To evaluate the potential impact of high-density planting as a yield-enhancing measure on soil health,the flue-cured tobacco variety Yunyan 99 was used as the material in this study,and two planting modes of conventional density and high density were established in the tobacco-growing area of Hanzhong,Shaanxi Province.Soil samples were collected from two soil layers of topsoil(0～10 cm)and subsoil(10～20 cm),and their physicochemical properties were analyzed.Illumina MiSeq high-throughput sequencing technology was used to study the structure of soil bacterial communities,and redundancy analysis(RDA)was used to explore the correlation between soil physicochemical factors and bacterial communities.The results showed that:①High-density planting significantly increased soil bulk density and moisture content,with higher values in the subsoil layer compared to the topsoil layer.②High-density planting led to significant soil acidification,and the contents of organic matter,total nitrogen,available nitrogen,total phosphorus,available phosphorus,total potassium,and available potassium all decreased,indicating that soil nutrient consumption increased.③High-density planting reduced the richness(number of species),species diversity and evenness of bacterial communities in different soil layers,and altered the vertical distribution pattern of bacterial communities with more in the topsoil and less in the subsoil.④High-density planting significantly reduced the relative abundance of Actinobacteria participated in organic matter metabolism and Proteobacteria involved in promoting nutrient cycling,and increased the relative abundance of Acidobacteria and Chloroflexi associated with barren soil environment.⑤High-density planting significantly increased the relative abundance of Norank_f__Norank_o__Vicinamibacterales that might promote tobacco disease susceptibility,and the relative abundance of RB41 and Norank_f__Vicinamibacteraceae that might promote soil acidification and reduce soil organic carbon in the topsoil,while reduced the relative abundance of Sphingomonas that could promote plant growth and inhibit plant pathogens.⑥RDA analysis showed that soil moisture content was significantly positively correlated with bacterial α diversity,and total nitrogen,pH,and available potassium were significantly positively correlated with bacterial community evenness.In summary,high-density planting of flue-cured tobacco not only alters soil physicochemical properties and microenvironment,causes soil acidification and accelerates nutrient depletion,but also drives the succession of soil bacterial communities towards to adapt to barren habitats,and may increase the risk of soil-borne diseases.The research results can provide a theoretical basis for scientifically evaluating the sustainability of this model and formulating corresponding soil management and microecological regulation strategies.

Cigar tobacco leaves were fermented using strong-flavor Baijiu,Saccharomyces cerevisiae cell suspension,its supernatant,and ethanol as fermentation media.The volatile flavor compounds in cigar tobacco leaves fermented with different media were determined with headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry,aiming to explore the specific pathways of ester synthesis by S.cerevisiae.Non-ester differential volatile flavor compounds were screened by principal component analysis(PCA),orthogonal partial least squares-discriminant analysis(OPLS-DA),and variable importance in projection(VIP),and sensory evaluation of the fermented tobacco leaves was conducted.The results showed that the content and variety of ester compounds in cigar tobacco leaves fermented with S.cerevisiae fermentation supernatant combined with ethanol were significantly increased compared to the original tobacco leaves(P<0.05).Among them,ethyl acetate(0.002 5 μmol/g)and ethyl hexadecanoate(0.002 5 μmol/g)were significantly enriched.The enhancement mechanism was attributed to exogenous esterase catalysis,ethanol-mediated substrate migration,and hydrophobic retention effects.This fermentation medium had no significant impact on key aroma components such as dihydroactinidiolide in cigar tobacco leaves.A total of 47 non-ester differential volatile flavor compounds,including phenethyl alcohol and n-hexanal,were screened.Sensory evaluation indicated that the aroma intensity,maturity,and other indicators of cigar tobacco leaves in the S.cerevisiae fermentation supernatant-ethanol co-fermentation group were significantly improved.This study provides microbial resources for developing cigar flavor-enhancing technology based on in-situ microbial fermentation.

[Objective]To investigate the material basis underlying the significant differences in color changes during the air-curing process of cigar tobacco leaves.[Method]Using middle leaves of cultivars Chuanxue No.5 and Dexue No.1 as experimental materials,changes in leaf images,color parameters,and cellular ultrastructure during curing were recorded.Ultra-high-performance liquid chromatography coupled with orbitrap mass spectrometry(UHPLC-OE-MS)was employed for metabolomic analysis of leaves on day 9 of curing.[Result]As curing progressed,yellowing and browning occurred faster in Chuanxue No.5 than in Dexue No.1.In the early curing stage,Chuanxue No.5 exhibited higher values for lightness(L*),yellowness/blueness(b*),and browning index(BI)compared to Dexue No.1.The L* and b* values of Chuanxue No.5 declined sharply after day 9,while BI differences diminished in mid-to-late curing.Ultrastructural analysis revealed earlier membrane rupture,chloroplast disintegration,and an increasing number of plastoglobules formation in Chuanxue No.5.Metabolomic profiling on day 9 identified significant inter-cultivar differences:Chuanxue No.5 showed higher overall relative content of lipids and lipid-like molecules.Further screening identified 40 significantly differential metabolites,primarily fatty acids,flavonoids,and terpenoids.KEGG enrichment analysis indicated that differentially abundant metabolites were most prominently enriched in linoleic acid metabolism and α-linolenic acid metabolism pathways.Among these,9(S)-HODE—a metabolic derivative of linoleic acid—exhibited higher relative abundance in Chuanxue No.5 leaves.[Conclusion]The differential progression of color changes during curing may be attributed to variations in the relative content of metabolites such as fatty acids and flavonoids.

The experiment aimed to screen high-yield cellulase strains and optimize the enzyme production process and enzymatic hydrolysis conditions.Through microbial screening techniques,a strain of Bacillus subtilis X-l was isolated.The enzyme production conditions and enzymatic hydrolysis conditions of the strain were optimized.The results showed that the optimized enzyme production conditions for the strain were 3％glucose,0.1％urea,10 mL/L trace element nutrient solution,6％inoculation amount,and 15 h of fermentation time.Under these conditions,the endoglucanase activity was 3.96 U/mL,the β-glucosidase activity was 3.77 U/mL,and the exoglucanase activity was 4.00 U/mL.The optimized enzymatic hydrolysis conditions were as follows:The optimal temperature for β-glucosidase and exoglucanase was 45 ℃,the optimal temperature for endoglucanase was 60 ℃,the enzymatic hydrolysis pH was 6～8,and the enzymatic hydrolysis time was 2.0～2.5 h.Under these conditions,the cellulase activity was the strongest.The study indicates that Bacillus subtilis X-l has the characteristic of high cellulase production.The optimized process in the experiment enhanced the enzyme production activity and degradation efficiency of the strain.The results can provide a reference for the resource utilization of high-cellulose waste.