Anaerobic digestion of tobacco stalk: biomethane production performance and kinetic analysis

Proteomic and Metabolomic Revealed Differences in the Distribution and Synthesis Mechanism of Aroma Precursors in Yunyan 87 Tobacco Leaf, Stem, and Root at the Seedling Stage

Tobacco, as an important cash crop and model plant, has been the subject of various types of research. The quality of flue-cured tobacco products depends on the compound collection of tobacco leaves, including pigments, carbohydrates, amino acids, polyphenols, and alkaloid aroma precursors. The present study investigates tobacco seedling organs (leaf, stem, and root) with the assistance of label-free proteomic technology and untargeted metabonomic technology. We analyzed 4992 proteins and 298 metabolites obtained in the leaf, stem, and root groups and found that there were significant differences in both primary and secondary metabolism processes involved in aroma precursor biosynthesis, such as carbohydrate metabolism, energy metabolism, and amino acid biosynthesis, and phenylpropanoid, flavonoid, and alkaloid biosynthesis. The findings showed that the contents of alkaloid metabolites such as nornicotine, anatabine, anatalline, and myosmine were significantly higher in tobacco roots than in leaves and stems at the seedling stage.

Anaerobic Co-digestion of Rice Straw and Pig Manure Pretreated With a Cellulolytic Microflora: Methane Yield Evaluation and Kinetics Analysis

Agricultural wastes, such as rice straw (RS) and pig manure (PM), cause serious environmental pollution due to the non-existence of effective disposal methods. Urgent investigations are needed to explore how such wastes can be transformed into resources. In this study, we comprehensively assessed methane yield and kinetics of RS and PM anaerobic co-digestion, with or without pretreatment of a previously developed cellulolytic microflora, under conditions of their maximum organic loading rate. The anaerobic co-digestion results revealed that the cumulative methane production of RS and PM after bio-pretreatment was 342.35 ml (g-VS)⁻¹, which is 45% higher than that of the control group [236.03 ml·(g-VS)⁻¹]. Moreover, the kinetic analysis showed the first-order kinetic, while the modified Gompertz models revealed higher fitting properties (R² ≥ 0.966). After bio-pretreatment, the hydrolytic constant, maximum accumulative methane production, and maximum methane production rates of RS and PM reached 0.46 day⁻¹, 350.79 ml·(g-VS)⁻¹, and 45.36 ml·(g-VS)⁻¹·day⁻¹, respectively, which were 77, 45.1, and 84.3% higher than those without pretreatment. Also, we found that the lag phase and effective methane production time after bio-pretreatment decreased from 2.43 to 1.79 days and 10.7 to 8.92 days, respectively. Upon energy balance evaluation, we reported a net energy output of 5133.02 kWh·ton⁻¹ after bio-pretreatment. Findings from this present study demonstrated that bio-pretreatment of RS and PM mixtures with cellulolytic microflora could greatly enhance methane production and anaerobic digestion efficiency.

Anaerobic digestion as a laboratory experiment for undergraduate biochemistry courses

Compared to aerobic catabolism, the theories and experiments of anaerobic catabolism are not covered in depth in biochemistry education curricula. Anaerobic digestion (AD) is a feasible method for converting common organic compounds to renewable energy-methane that has drawn a great deal of attention in practical applications. In this study, we designed an AD laboratory experiment for use in undergraduate biochemistry courses to supplement the knowledge of metabolic networks in biochemistry and extend the information presented in biochemistry textbooks. In this laboratory experiment, students explored the methane production performance of wheat straw (WS; a representative and commonly available agricultural waste) and mastered a reasonable method for utilizing this new biochemical reaction to convert organic wastes from renewable resources to methane. Basic experimental procedures, such as a biochemical methane potential (BMP) assay, data analysis, and graphic presentations were organized to provide students with abundant hands-on experience. Furthermore, calculations of significant parameters, such as total solids (TS), volatile solids (VS), experimental methane yield (EMY), maximum theoretical methane production (MMP), and biodegradability (B_D ), were also performed. From this AD experiment, students learned not only a new series of biochemical reactions but also a novel strategy to achieve cleaner methane production from organic wastes, exhibiting a positive impact for students' learning in biochemistry course.

Porous carbon from tobacco stalk for removal of organic dyes from water

Tobacco stalk, a kind of agricultural residue, will cause environmental pollution because it contains some harmful substances such as nicotine. To realize the high-value utilization of this agricultural residue, we prepared porous carbon (TS-C) by high temperature carbonization using tobacco stalk as a precursor. It was found that TS-C displays a hierarchical pore structure and high Brunauer–Emmett–Teller (BET) surface area of 1416 m² g⁻¹. Moreover, TS-C has excellent performance in organic dye adsorption at room temperature, especially for Gentian violet (GV), with the maximum adsorption capacity of 926 mg g⁻¹.

Harmful organic dyes in water can be removed by porous carbon from hazardous tobacco stalk.