Journal Applied Environmental Biotechnology-
Published: 25 November 2018
Applied Environmental Biotechnology, Volume 3, pp 1-4; doi:10.26789/aeb.2018.02.006
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.
Published: 1 January 2018
Applied Environmental Biotechnology, Volume 3, pp 1-22; doi:10.26789/aeb.2018.02.002
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.
Published: 1 January 2018
Applied Environmental Biotechnology, Volume 3, pp 1-8; doi:10.26789/aeb.2018.02.001
Abstract:The lactic acid bacteria (LAB) play a crucial role in the health of aquatic animals through controlling and competing with pathogens. In this study, based on the high-throughput sequencing of 16S rRNA gene amplicons, we examined the LAB in the gut of freshwater shrimp (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 gut. In addition, share and unique LAB among the shrimp gut, 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 gut 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 gut and their environments and further improving the ecological management of aquatic ecosystems regarding the application of probiotics and disease prevention.
Published: 1 January 2018
Applied Environmental Biotechnology, Volume 3, pp 1-7; doi:10.26789/aeb.2018.02.005
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.
Published: 1 January 2018
Applied Environmental Biotechnology, Volume 3, pp 1-9; doi:10.26789/aeb.2018.02.004
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.
Published: 31 October 2017
Applied Environmental Biotechnology, Volume 2; doi:10.26789/AEB.2017.01.006
Abstract:Degradation of syndiotactic poly([R]-b-hydroxybutyrate) (syn-PHB), a chemically synthesized PHB, was investigated in this study by incubation polymer films in a soil of northeastern China. During incubation, progressive weight loss of the syn-PHB films and a corresponding decrease of molecular weight were observed over the 90 days of incubation indicating the biodegradation of syn-PHB and the random cleavage of ester bonds. Microorganisms isolated and identified from the partially degraded films included Pseudomonas spp., Alcaligenese sp., and Comamonas sp. Our results suggest that chemically synthesized syn-PHB is biodegradable under aerobic conditions in soil.
Published: 29 September 2017
Applied Environmental Biotechnology, Volume 2; doi:10.26789/AEB.2017.01.005
Abstract:Nanocellulose has many advantages, such as a wide range of sources of raw materials, renewability, biodegradability, high aspect ratio and large specific surface area. It can be potentially used in medicine, electronics, information technology, energy industry, aerospace and some other high-technological fields. For preparation of nanocellulose, it is particularly important to separate nanocellulose from raw materials by an environment-friendly method with environmental protection awareness. Consequently, we here report an effective and environmental friendly method to isolate nanocellulose from a shrub plant, i.e., Amorpha fruticosa Linn. Firstly, the plant fiber is pretreated with chemicals to remove lignin and hemicellulose; then the derived purified cellulose is pretreated with enzyme hydrolysis, followed by slight treatment of high-pressure homogenization. The results showed that with the assistance of enzyme pretreatment, effective isolation of nanocellulose could be achieved, resulting in materials with a uniform diameter distribution and an average value of about 10 nm. The aspect ratio of the derived nanocellulose is greater than 1000. Such results showed that the method was green and effective for nanocellulose isolation, and the derived biomaterial as a unique biocompatible and high-strength biomass nanomaterial could be used in biomedical, environmental protection and other fields.
Published: 25 September 2017
Applied Environmental Biotechnology, Volume 2; doi:10.26789/AEB.2017.01.004
Abstract:Responses of phenolic compounds was hydroponically investigated in rice seedlings (Oryza sativa L. cv. XZX 45) treated with either Cr(III) or Cr(VI). Results indicated that rice seedlings are able to effectively sequester both species of Cr. Majority of Cr recovered in plant materials was accumulated in roots rather than shoots. Accumulation of total soluble phenolics, flavonoids and lignin in plant materials was quite evident due to Cr exposure, but displaying different responses between the two species of Cr. Distribution of total soluble phenolics and flavonoids was more at shoots, especially at younger segments of shoots, and less at roots, whereas the lignin content was detected more at the younger parts of shoots and less towards the root tips. It is suggestive from the current investigation that both Cr species caused production and accumulation of these secondary metabolites in rice seedlings.
Published: 25 September 2017
Applied Environmental Biotechnology, Volume 2; doi:10.26789/AEB.2017.01.008
Abstract:Biodegradation of plastics as a research topic has received increasing attention due to their recalcitrant nature and large quantities, but little progresses and new information have been made available recently in the literature. In this context, plastics properties as a substrate, microorganisms responsible for degradation, assessment techniques and degradability are discussed critically to summarize the basic requirements for proper biodegradation testing and also the interpretation of the results for a meaningful presentation. New directions in this area of research are also presented to individuals working on this topic to advance the research.
Published: 24 September 2017
Applied Environmental Biotechnology, Volume 2; doi:10.26789/AEB.2017.01.002
Abstract:Ammonia oxidation is an important step of the nitrogen cycle and was considered to be conducted only by ammonia-oxidizing bacteria (AOB) for a long time. The discovery of ammonia-oxidizing archaea (AOA) caused consideration of the relative contributions of these two functional groups in different niches and factors resulting in their niche segregation. Previous studies showed that some environmental factors may correlate to the abundance and distribution of AOA and AOB, including ammonia/ammonium concentration, pH, organic matters, oxygen concentration, temperature, salinity, sulfide concentration, phosphate concentration, soil moisture, and so on. Despite extensive studies conducted on ecology of AOA and AOB to find key environmental factors dominating niche segregation between AOA and AOB, few studies were conducted to explore the interrelationship among environmental factors. In this review, five main environmental factors which may be related to each other were selectively reviewed independently, including ammonia concentration, pH, temperature, oxygen concentration and organic matters. Furthermore, potential interrelationship among environmental factors was proposed.