Application of pectin hydrolyzing bacteria in tobacco to improve flue-cured tobacco quality.

To study the relationship between the diversity of the surface microbial community and tobacco flavor, and to improve tobacco quality using microorganisms. The microbial community composition and diversity of 14 samples of flue-cured tobacco from tobacco-producing areas in Yunnan with varying grades were analyzed by high-throughput sequencing. PICRUSt was used for predicting microbial functions. A strain of Bacillus amyloliquefaciens W6-2 with the ability to degrade pectin was screened from the surface of flued-cured tobacco leaves from Yunnan reroasted tobacco leave. The enzyme preparation was prepared through fermentation and then applied for treating flue-cured tobacco. The improvement effect was evaluated by measuring the content of macromolecule and the changes in volatile components, combined with sensory evaluations. The bacterial communities on the surface of flue-cured tobacco exhibited functional diversity, consisting primarily of Variovorax, Pseudomonas, Sphingomonas, Burkholderia, and Bacillus. These bacterial strains played a role in the aging process of flue-cured tobacco leaves by participating in amino acid metabolism and carbohydrate metabolism. These metabolic activity converted complex macromolecules into smaller molecular compounds, ultimately influence the smoking quality and burning characteristics of flue-cured tobacco. The pectinase preparation produced through fermentation using W6-2 has been found to enhance the aroma and sweetness of flue-cured tobacco, leading to improved aroma, reduced impurities, and enhanced smoothness. Additionally, the levels of pectin, cellulose, and hemicellulose decreased, while the levels of water-soluble sugar and reducing sugar increased, and the contents of esters, ketones, and aldehydes increased, and the contents of benzoic acid decreased. The study revealed the correlation between surface microorganisms and volatile components of Yunnan tobacco leaves, and the enzyme produced by the pectin-degrading bacteria W6-2 effectively improved the quality of flue-cured tobacco.

Complete genome analysis of Bacillus subtilis TY-1 reveals its biocontrol potential against tobacco bacterial wilt.

Bacillus subtilis TY-1 was isolated from 2000 m-deep sea sediments of the Western Pacific Ocean, which was found to exhibit strong antagonistic activity against tobacco bacterial wilt caused by Ralstonia solanacearum. Here, we present the annotated complete genomic sequence of the strain Bacillus subtilis TY-1. The genome consists of a 4,030,869-bp circular chromosome with a G + C content of 43.88%, 86 tRNAs, and 30 rRNAs. Genomic analysis identified a large number of gene clusters involved in the biosynthesis of antibacterial metabolites, including lipopeptides(surfactin, bacillibactin, and fengycin) and polyketides(bacillaene). Meanwhile, numerous genes encoding carbohydrate-active enzymes and secreted proteins were found in TY-1. These findings suggest that Bacillus subtilis TY-1 appears to be a potential biocontrol agent against tobacco bacterial wilt in agricultural fields.

Diffusion-layer-free air cathode based on ionic conductive hydrogel for microbial fuel cells.

High hydraulic pressure in air-cathode microbial fuel cells (MFCs) can lead to severe cathodic water leakage and power reduction, thereby hindering the practical applications of MFCs. In this study, an alternative air cathode without a diffusion layer was developed using a cross-linked hydrogel, oxidized konjac glucomannan/2-hydroxypropytrimethyl ammonium chloride chitosan (OKH), for ion bridging. The cathode was placed horizontally to avoid hydraulic pressure on its surface. Ion transportation was sustained with a minimal OKH hydrogel loading of 10 mg/cm2. A maximum power density of 1.0 ± 0.04 W/m2 was achieved, which was only slightly lower than the 1.28 ± 0.02 W/m2 of common air cathodes. Moreover, the cost of the OKH hydrogel is only $0.12/m2, which can reduce ~85% of the cathode cost without using the advanced polyvinylidene fluoride diffusion layer. Therefore, the development of this new diffusion-layer-free air cathode using conductive ionic hydrogel provides a low-cost strategy for stable MFC operation, thereby demonstrating great potential for practical applications of MFC technology.

High tolerance of and removal of cefazolin sodium in single-chamber microbial fuel cells operation.

Single-chamber microbial fuel cells (MFCs) have been shown to be a promising approach for cefazolin sodium (CFZS)-contaminated wastewater treatment, in terms of electricity production, high CFZS tolerance and effective CFZS removal. MFCs exposed to CFZS loadings up to 100 mg L-1, produced stable power of 18.2 ±â€¯1.1 W m-3 and a maximum power of 30.4 ±â€¯2.1 W m-3, similar to that of CFZS-free MFCs (stable power 19.4 ±â€¯0.8 W m-3 and maximum power 32.5 ±â€¯1.6 W m-3), notwithstanding a longer acclimitisation MFC activation. More anodophilic genera (i.e. Acinetobacter, Stenotrophomonas, Lysinibacillus) and antibiotic-resisting genera (i.e. Dysgonomonas) were enriched in CFZS acclimitised anodes. Both the thickness of biofilms and the duration of CFZS acclimitisation were essential for the development of high CFZS tolerance (e.g. 450 mg L-1). The inhibition of MFCs by CFZS was reversible. The present MFCs generated a CFZS removal rate of 1.2-6.8 mg L-1 h-1 without any apparent inhibition of electricity production.

Efficient removal of nitrobenzene and concomitant electricity production by single-chamber microbial fuel cells with activated carbon air-cathode.

Single-chamber microbial fuel cells (S-MFCs) with bio-anodes and activated carbon (AC) air-cathodes showed high nitrobenzene (NB) tolerance and NB removal with concomitant electricity production. The maximum power over 25Wm-3 could be obtained when S-MFCs were operated in the NB loading range of 1.2-6.2molm-3d-1, and stable electricity production over 13.7Wm-3 could be produced in a NB loading range of 1.2-14.7molm-3d-1. The present S-MFCs exhibited high NB removal performance with NB removal efficiency over 97% even when the NB loading rate was increased to 17.2molm-3d-1. The potential NB reduced product (i.e. aniline) could also be effectively removed from influents. The findings in this study means that single-chamber MFCs assembled with pre-enriched bio-anodes and AC air-cathodes could be developed as effective bio-electrochemical systems to remove NB from wastewaters and to harvest energy instead of consuming energy.

Acclimatization of microbial consortia to alkaline conditions and enhanced electricity generation.

Air-cathode microbial fuel cells (MFCs), obtained by inoculating with an aerobic activated sludge, were activated over a one month period, at pH 10.0, to obtain alkaline MFCs. The alkaline MFCs produced stable power of 118mWm(-2) and a maximum power density of 213mWm(-2) at pH 10.0, using glucose as substrate. The performance of the MFCs was enhanced to produce a stable power of 140mWm(-2) and a maximum power density of 235mWm(-2) by increasing pH to 11.0. This is the highest pH for stably operating MFCs reported in the literature. Power production was found to be suppressed at higher pH (12.0) and lower pH (9.0). Microbial analysis indicated that Firmicutes phylum was largely enriched in the anodic biofilms (88%), within which Eremococcus genus was the dominant group (47%). It is the first time that Eremococcus genus was described in bio-electrochemical systems.

Riboflavin-shuttled extracellular electron transfer from Enterococcus faecalis to electrodes in microbial fuel cells.

Great attention has been focused on Gram-negative bacteria in the application of microbial fuel cells. In this study, the Gram-positive bacterium Enterococcus faecalis was employed in microbial fuel cells. Bacterial biofilms formed by E. faecalis ZER6 were investigated with respect to electricity production through the riboflavin-shuttled extracellular electron transfer. Trace riboflavin was shown to be essential for transferring electrons derived from the oxidation of glucose outside the peptidoglycan layer in the cell wall of E. faecalis biofilms formed on the surface of electrodes, in the absence of other potential electron mediators (e.g., yeast extract).

Enhanced electricity production by use of reconstituted artificial consortia of estuarine bacteria grown as biofilms.

Microbial fuel cells (MFCs) can convert organic compounds directly into electricity by catalytic oxidation, and although MFCs have attracted considerable interest, there is little information on the electricity-generating potential of artificial bacterial biofilms. We have used acetate-fed MFCs inoculated with sediment, with two-chamber bottles and carbon cloth electrodes to deliver a maximum power output of ~175 mW · m(-2) and a stable power output of ~105 mW · m(-2). Power production was by direct transfer of electrons to the anode from bacterial consortia growing on the anode, as confirmed by cyclic voltammetry (CV) and scanning electron microscopy (SEM). Twenty different species (74 strains) of bacteria were isolated from the consortium under anaerobic conditions and cultured in the laboratory, of which 34% were found to be exoelectrogens in single-species studies. Exoelectrogenesis by members of the genera Vibrio , Enterobacter , and Citrobacter and by Bacillus stratosphericus was confirmed, by use of culture-based methods, for the first time. An MFC with a natural bacterial consortium showed higher power densities than those obtained with single strains. In addition, the maximum power output could be further increased to ~200 mW · m(-2) when an artificial consortium consisting of the best 25 exoelectrogenic isolates was used, demonstrating the potential for increased performance and underlying the importance of artificial biofilms for increasing power output.

Study of inclusion complex of beta-cyclodextrin and nitrobenzene.

beta-cyclodextrin can react with nitrobenzene to form an inclusion complex which is characterized by (1)H NMR and powder X-ray diffractometry. The ratio of beta-CD to NB in inclusion complex is determined as 1:1. At 25 degrees C, the dissociated constant, K(D), of the inclusion complex is measured as 6.5 x 10(-3) M in neutral solution (pH=7.0), but in alkali (pH=13.5), K(D) is 3.2 x 10(-2) M which is much larger than that measured in neutral.