Vol 3, No 2 (2018)

Table of Contents

EDITORIAL

181 Views, 81 PDF Downloads
Ji-Dong Gu
DOI:10.18063/AEB.2016.01.001

Abstract

N/A

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RESEARCH ARTICLES

352 Views, 19 PDF Downloads
Lin Na Du, Ke Ke Pan, Gang Li, Yu Yi Yang, Fang Cheng Xu

Abstract

Microbial decolorization has been investigated extensively. Various microbes have been studied for their dye removing capability; however, microbial decolorizer with a strong environmental adaptability and wide substrate spectrum is of great potential for its possible practical application. Therefore, in this study, Aeromonas sp. DH-6, a wide dye spectrum decolorizer, was investigated in terms of its use for Malachite Green (MG) remediation. Results indicated that most of carbon sources have no effect on decolorization, while the nitrogen sources of beef extract and yeast extract could enhance MG decolorization significantly. Among the tested metal ions, Cu2+, Fe2+, and Zn2+ could significantly inhibit decolorization. Moreover, the strain showed a very stable and efficient decolorization performance in the pH of 5.0-10.0 and at 20-40oC. Besides, it could almost completely decolorize MG at concentrations ≤ 1000 mg/L within 36 h. Based on UV-visible, GC-MS, and FTIR analysis, biodegradation of MG by the strain DH-6 was confirmed and data showed that MG was decomposed into 4-(Dimethylamino)benzophenone and other metabolites containing –C=O, –NH, and –OH groups. Enzyme analysis showed that tyrosinase, laccase, LiP, NADH-DCIP reductase, and MG reductase might be involved in MG degradation by the strain DH-6. Overall, the results demonstrated that the strain DH-6 will have an effective use as an alternative in MG bioremediation.


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51 Views, 5 PDF Downloads
Yan-Ting Zhao, Lin Ye, Cui-Lan Duan, Xu-Xiang Zhang

Abstract

The lactic acid producing bacteria (LAB) play a crucial role in the health of aquatic animals through controlling and competing against pathogens. In this study, based on the high-throughput sequencing of 16S rRNA gene amplicons, we examined the LAB in the gut of freshwater shrimps (Macrobrachium nipponense) and their living environments (sediment and pond water) and analyzed the correlations between the shrimp production and abundance of LAB. A high diversity and abundance of LAB (27 genera) were observed among the freshwater shrimp gut samples, and the results indicated that dissolved oxygen and temperature could affect the LAB community in the shrimp guts. In addition, shared and unique LAB among the shrimp guts, sediment and pond water were further analyzed. Linear regression analysis showed that the relative abundance of LAB was positively correlated with the levels of shrimp production. Moreover, comparison of the LAB community among different animals indicated that some LAB in shrimp guts may also play a beneficial role in fish, houseflies, pig and other animals. Collectively, this study provides comprehensive information for better understanding LAB in shrimp guts and their environments and further improving the ecological management of aquatic ecosystems regarding the application of probiotics and disease prevention.


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151 Views, 43 PDF Downloads
Chen-yang Li, Fang-Fang Liu, Jiang Ye, Jin-Feng Liu, Shi-Zhong Yang, Hui-Zhan Zhang, Bo-Zhong Mu

Abstract

A low-temperature active endo-β-1,4-mannanase (YBMan) from Bacillus subtilis TD7 was isolated, characterized and successfully expressed in Escherichia coli to enhance the yield of mannanase for a potential application as a gel-breaker in guar gum-based fracturing fluids in oilfields. YBMan showed good compatibility with a wide temperature range and retained about 70% relative activity at 20°C compared to its optimal temperature (65°C). This is the highest relative activity among reported low-temperature active mannanases against guar gum. The gene (1104 bp) of strain TD7 coding a protein with 367 amino acid residues was cloned and its expression generated two recombinant mannanases, TBMan-1 and TBMan-2. Compared to the wild type, the protein yield of TBMan-1 from a one-liter shake flask broth increased 5.6-fold, and the specific activity (crude enzyme) increased 6.4-fold. The total enzyme activity increased 35.8-fold with a total activity of approximately 79550 U. Moreover, TBMan-1 had at 20°C still about 80% relative activity. The enzyme was evaluated also for its application as gel-breaker and showed excellent ability for viscosity reduction with guar gum at 20°C. Low-temperature activity and high yield make the recombinant β-mannanase attractive for applications with guar-based hydraulic fracturing fluids and other biotechnological aspects.

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REVIEW ARTICLES

137 Views, 10 PDF Downloads
Ji-Dong Gu

Abstract

Coastal ecosystem is important because it bridges ocean and land. The brackish water receiving nutrients originated from land may nourish heterotrophic bacteria including Vibrio species, some of which may pose potential hazards to the public, marine lives and migratory birds in the coastal environment. A rich diversity of Vibrios is evident in the coastal and open oceans, but information on their ecophysiological adaptation and survival is still very limited. Their important roles in the geobiochemical cycles of nutrients have not been exolored adequately. In addition, it also been recently discovered that these Vibrios harbor a very rich of plasmids of various sizes with little knowledge on their function to the hosts. This information deserves attention in Vibrio ecology and their role in the various ecosystems for a better understanding of their survival and physiological function. 


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COMMENTARY

94 Views, 75 PDF Downloads
Ji-Dong Gu

Abstract

Pollution of soils and sediments by metals and metalloids is a serious environmental problem and threat to the ecological health and environmental quality. Microorganisms are known capable of detoxifying metals and metaloids into insoluble or non-bioavailable forms so that bioaccumualtion can be prevented under selective conditions. A key issue involved in bioremediation is the very poor understanding on the chemistry of the pollutants, specifically the bioavailable concentartions of metals and metalloids in the environmental matrices, especially soils and sediments and at the relevant pH value. Chemical states of the pollutants in terms of speciation are crucial to the possible success of any remediation practice, but it is impossible to conduct an effective operation for cleaning up without such information in mind. In the literature available, it is a common trend and practice to justify bioremediation for in situ application by using pure cultures of microorganisms, but this is a very prematured and bold attempt to applying microorganisms for in situ cleaning up without any scientific ground to support. For polluted soils and sediments, microorganisms have no role for cleaning up but phytoremediation is an effective means to remove and extract toxic metals and metallods from the complex soil matrices. This has been demonstrated successfully with a number of metals and organics as well as organic pollutants in both laboratory and also field trials.


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