Zhihui Bai

Progress in decontamination by halophilic microorganisms in saline wastewater and soil.

Environments with high-salt concentrations are often populated by dense microbial communities. Halophilic microorganisms can be isolated from different saline environments and different strains even belonging to the same genus have various applications. Wastewater and soil rich in both organic matter and salt are difficult to treat using conventional microorganisms typically found in wastewater treatment and soil bioremediation facilities. Studies on decontaminative capabilities and decontamination pathways of organic contaminants (i.e., aromatic compounds benzoate, cinnamate, 3-phenylpropionate, 4-hydroxybenzoic acid), heavy metals (i.e., tellurium, vanadium), and nutrients in the biological treatment of saline wastewater and soil by halophilic microorganisms are discussed in this review.

The impacts of cypermethrin pesticide application on the non-target microbial community of the pepper plant phyllosphere.

Although pesticides have been extensively used for controlling insects and disease pathogens of plants, little is known regarding the impacts of applying these pesticides on the microbial community in the plant phyllosphere. Here, we report the effects of cypermethrin pesticide application upon the microbial community of the pepper plant phyllosphere. Assessments were made using culture-independent techniques including phospholipid fatty acid analysis (PLFA) and 16S rRNA gene directed Polymerase Chain Reaction with Denaturing Gradient Gel Electrophoresis (PCR-DGGE). During the 21 day greenhouse study, PLFA results indicated that both total and bacterial biomass increased after application of the pesticide. PLFA profiles also indicated that Gram-negative bacteria became predominant. DGGE analysis confirmed a significant change in bacterial community structure within the phyllosphere following the pesticide application where different dendrogram clusters were observed between control and treated samples. Phylogenetic analysis also suggested a change in bacterial phyla following treatment, where bands sequenced within control cultures were predominantly of the Firmicutes phylum, but those bands sequenced in the treated samples were predominantly members of the Bacteroidetes and gamma-Proteobacteria phyla. In conclusion, this study revealed an increase in bacterial abundance and a shift in community composition within the pepper plant phyllosphere following the pesticide application, and highlighted the effective use of PLFA and PCR-DGGE for studying the effect of pesticides upon indigenous phyllosphere microbes.

Biodegradation of di-n-butyl phthalate by an isolated Gordonia sp. strain QH-11: Genetic identification and degradation kinetics

Di-n-butyl phthalate (DBP) is one of the most widely used phthalic acid esters (PAEs), which have shown increasing environmental concerns worldwide. A bacterial strain designated as QH-11, was isolated from activated sludge and found to be capable of utilizing DBP as carbon and energy sources for growth. 16S rRNA and gyrb gene sequence analysis revealed that strain QH-11 was most closely related to Gordonia sp. Kinetics studies of DBP degradation by the strain QH-11 revealed that DBP depletion curves fit with the modified Gompertz model (R(2)>0.98). Meanwhile, substrate utilization tests showed that strain QH-11 could utilize other common PAEs and also the main intermediate product phthalic acid (PA). A gene encoding the large subunit of the phthalate dioxygenase, which is responsible for PA degradation, was successfully detected in strain QH-11. Furthermore, the results of reverse transcription quantitative PCR demonstrate that mRNA expression level of phthalate dioxygenase increased significantly after strain QH-11 was induced by DBP and PA.

Assessing the impact of the biological control agent Bacillus thuringiensis on the indigenous microbial community within the pepper plant phyllosphere.

Although biological control agents (BCAs) have been used extensively for controlling insects and pathogens of plants, little is known regarding the effects of such agents on the indigenous microbial communities within the plant phyllosphere. We assessed the effect of the BCA Bacillus thuringiensis (Bt) on the microbial communities within the pepper plant phyllosphere using culture-independent methodologies. Phospholipid fatty acid (PLFA) analysis suggested that the bacterial and fungal biomass were not significantly affected following Bt application. However, principal component analysis of PLFA data indicated that Bt did change the phyllosphere microbial community structure significantly. 16S rRNA gene-directed PCR with denaturing gradient gel electrophoresis (DGGE) also suggested a significant change in the phyllosphere bacterial community structure following Bt inoculation. Phylogenetic analysis of excised DGGE bands suggested a change in bacterial phyla; bands from untreated samples predominantly belonged to the Firmicutes, while Gammaproteobacteria abounded in the treated samples.

Utilization of winery wastes for Trichoderma viride biocontrol agent production by solid state fermentation.

Biocontrol agents are safe and environmental friendly alternatives for pesticides in agriculture application. Trichoderma viride WEBL0703 performed a high level of antagonistic activity toward a broad spectrum of phytopathogens and was determined as a biocontrol agent, which was produced by solid state fermentation using grape marc and wine lees. The maximum yield of T. viride conidia was up to 6.65 x 10(9) CFU/g initial dry substrate (IDS) after 10 d fermentation. As important enzymes for protecting plants from disease, chitinase, beta-glucanase, and pectinase yields were 47.8 U/g IDS, 8.32 U/g IDS and 9.83 U/g IDS, respectively. These results show that it is feasible to convert winery wastes to a value-added and environmental friendly biocontrol agent.

Effect of cypermethrin insecticide on the microbial community in cucumber phyllosphere

Cucumber (Cucumis sativus) is one of the most widely used vegetable in the world, and different pesticides have been extensively used for controlling the insects and disease pathogens of this plant. However, little is known about how the pesticides affect the microbial community in cucumber phyllosphere. This study was the first attempt to assess the impact of pyrethroid insecticide cyperemethrin on the microbial communities of cucumber phyllosphere using biochemical and genetic approaches. Phospholipid fatty acid (PLFA) assay indicated that cyperemethrin insecticide treatment led to a significant increase in both total and bacterial biomass and a decrease in fungal biomass and the ratio of Gram-positive (GP) bacteria to Gram-negative (GN) bacteria within the cucumber phyllosphere. Principal-component analyses (PCA) suggested that the number of unsaturated and cyclopropane PLFAs (16:1 omega 9t, 18:1 omega 7, cy17:0, cy19:0) increased with the insecticide treatment, whereas the saturated PLFA i16:0, i17:0 decreased. The increase of GN bacteria implied that the cypermethrin insecticide might be a nutrient for the growth of these phyllosphere microbes. Terminal restriction fragment length polymorphism (T-RFLP) reinforced the PLFA results. A significant change of bacterial community structure was observed in the separate dendrogram cluster between control and treated samples with the cucumber phyllosphere following cypermethrin insecticide treatment. Moreover, the increased terminal restriction fragments (T-RFs) (58, 62, 89, 99, 119, 195, 239, 311, 340, and 473 bp) indicated that some bacteria might play a significant role in the insecticide degradation within the cucumber phylosphere, whereas the disappeared T-RFs (44, 51, 96, 223, 306, and 338 bp) implied that some other bacteria might potentially serve as microbial indicator of cyperemethrin insecticide exposure.

Functional assembly of bacterial communities with activity for the biodegradation of an organophosphorus pesticide in the rape phyllosphere

Although most pesticides sprayed on terrestrial plants remain on their leaf surfaces, the relationship between leaf-associated microbial populations and pesticide degradation remains unclear. Here we examined changes in the bacterial community composition in the rape phyllosphere after treatment with dichlorvos, an organophosphorus pesticide. Results indicate that the bacterial community showed marked changes after treatment. We evaluated the rate of dichlorvos degradation by a natural microbial community on rape leaves and found that more dichlorvos was degraded on microbial-population-inhabited leaves than on surface-sterilized leaves. Six dichlorvos-degrading bacteria with 16S rRNA gene sequences that are most similar to those of members of the genera Pseudomonas, Xanthomonas, Sphingomonas, Acidovorax, Agrobacterium and Chryseobacterium were isolated from the natural community. We report for the first time that three of these epiphytic bacterial species, from the genera Sphingomonas, Acidovorax and Chryseobacterium, can degrade organophosphorus compounds. Collectively, these results provide direct evidence that bacteria on leaves can degrade organophosphate pesticides, and demonstrate that phyllosphere bacteria have great potential for the bioremediation of pesticides in situ, where the environment is hostile to nonepiphytic bacteria.

Biodegradation of Di-n-Butyl Phthalate by a Newly Isolated Halotolerant Sphingobium sp.

A Gram-negative strain (TJ) capable of growing aerobically on mixed phthalate esters (PAEs) as the sole carbon and energy source was isolated from the Haihe estuary, Tianjin, China. It was identified as belonging to the Sphingobium genus on the basis of morphological and physiological characteristics and 16S rRNA and gyrb gene sequencing. The batch tests for biodegradation of di-n-butyl phthalate (DBP) by the Sphingobium sp. TJ showed that the optimum conditions were 30 °C, pH 7.0, and the absence of NaCl. Stain TJ could tolerate up to 4% NaCl in minimal salt medium supplemented with DBP, although the DBP degradation rates slowed as NaCl concentration increased. In addition, substrate tests showed that strain TJ could utilize shorter side-chained PAEs, such as dimethyl phthalate and diethyl phthalate, but could not metabolize long-chained PAEs, such as di-n-octyl phthalate, diisooctyl phthalate, and di-(2-ethyl-hexyl) phthalate. To our knowledge, this is the first report on the biodegradation characteristics of DBP by a member of the Sphingobium genus.

Analysis of bacterial community in bulking sludge using culture-dependent and -independent approaches.

The bacterial community of a bulking sludge from a municipal wastewater treatment plant with anoxic-anaerobic-oxic process was investigated by combination of cultivation and 16S rRNA gene clone library analysis for understanding the causes of bulking. A total of 28 species were obtained from 63 isolates collected from six culture media. The most cultivable species belonged to gamma-Proteobacteria including Klebsiella sp., Pseudomonas sp., Aeromonas sp. and Acinetobacter sp. Further analysis of these strains by repetitive sequence based on polymerase chain reaction (rep-PCR) technology showed that rep-PCR yielded discriminatory banding patterns within the same genus using REP and BOX primer sets. While the culture-independent assessment revealed that beta-Proteobacteria was the dominant group in the bulking sample. Sequence analysis revealed that the highest proportion (14.7%) of operational taxonomic units was 98% similar to Candidatus Accumulibacter phosphatis, which is used to remove phosphorous from wastewater. Our results indicated that combining different approaches can produce complementary information, thus generate a more accurate view of microbial community in bulking sludge.

Biofuels from food processing wastes

Food processing industry generates substantial high organic wastes along with high energy uses. The recovery of food processing wastes as renewable energy sources represents a sustainable option for the substitution of fossil energy, contributing to the transition of food sector towards a low-carbon economy. This article reviews the latest research progress on biofuel production using food processing wastes. While extensive work on laboratory and pilot-scale biosystems for energy production has been reported, this work presents a review of advances in metabolic pathways, key technical issues and bioengineering outcomes in biofuel production from food processing wastes. Research challenges and further prospects associated with the knowledge advances and technology development of biofuel production are discussed.