On Enrichment Culturing and Transferring Technique

Enrichment culturing and transferring technique is frequently used to obtain specific functional microorganisms for more in-depth investigations from the complex samples containing a wide range of different microorganisms. This technique is fundamental and critically important in research of microbial ecology, environmental microbiology, and environmental science, but the proper practice of this technique in applications remains ambiguous to some investigators. Because of this situation, misuse and lack of comprehensive understanding of the meaning of this technique are frequently found in manuscripts or even publications. This article provides a discussion about this technique and the meaning for practical use to enhance research for high-quality results and the scientific information effectively when used. The key elements of this technique include, cultural medium composition, culturing and incubation, frequency of transferring for enrichment, procedures prior to the isolation and purification to obtain possibly pure cultures or enrichments of the capable microorganisms for further biochemistry and physiology investigations. The information is intended to improve the basic understanding of this technique for a more effective and efficient applications in research to advance the basic and fundamental information and to pave the way for more innovative research and discoveries to science.

On Environmental Biotechnology of Bioremediation

Environmental biotechnology (EB) can play positive and an important role in detoxifying and eliminating pollutants, and cleaning up the contaminated sites of ecosystems, but the development of any EB is based largely on the scientific knowledge and results of (micro)biology and chemistry, and then application mainly on engineering and management. Biodegradation and bioremediation by definition are different in meaning and, as a result, they must be treated differently. On the fundamental basis, the biochemical reactions and the biochemical degradation pathway of any targeted toxicant concerned are basic information before the degradability of the selective pollutant by a microorganism can be claimed. Bioremediation becomes feasible for implementation with the knowledge of the biochemical reactions by the biological agent coupling with the engineering and management to achieve a successful attempt at a site. Though the degradability by a microorganism can be achieved in laboratory condition, the cleaning up of the pollutant at any site needs additional information and knowledge of the physical, chemical and ecological characteristics of the site to allow any success to be achieved. The broad EB can include utilization of pure and selective microorganisms, the biochemical reactions by either pure or mixed culture, enzymes, and metabolic products of microorganisms. In addition, microorganisms may also work in the form of biofilm to carry out the function to detoxify the toxic environmental chemicals. In addition to microorganisms, plants can play an important role in phytoremediation. Overall, environmental biotechnology needs at least three steps to prove its effectiveness from concept testing in laboratory, establishment of the mechanisms involved, workability in complex system and ecosystems, and lastly the implementation and practice on site. A laboratory success on degradation cannot be quickly and simply treated as a claim of EB for bioremediation for application.

Characterization of Lignocellulosic Fibers Reinforced with Poly(vinyl alcohol)

The demands for materials made of plastics are rapidly increasing, especially in food packaging application. Recently, attention has been drawn to the use of bio-reinforced composites in packaging, automotive, medical and construction applications due to increased concern for environmental sustainability. Poly(vinyl alcohol) (PVA) films reinforced with crystals (unbleached) prepared by solution casting method possessed significantly improved properties compared to film reinforced with cellulose (bleached). From the results, PVA films with the addition of 4% (w/w) of crystalline cellulose exhibited best combination of properties. In addition to good mechanical properties, this composite has good water resistance and biodegradability. The water absorption of biocomposite was found to be 22.63%. From X - ray diffraction (XRD) analysis, diffraction peaks of biocomposite was observed at 2θ = 22.4384. From scanning electron microscopy (SEM) analysis it was found that fractures at surfaces of biocomposite film were smooth and even without any porosity and uniform dispersion of jute crystals in the matrix.

Cattle manure DOM on adsorption of copper by the cyanobacterium Aliinostoc species

Dissolved organic matter (DOM) and Cu(II), originated from livestock manure, often co-exist in livestock effluents. The effects of DOM on adsorption of Cu(II) by adsorbent remain unknown, which may prevent the removal of Cu(II) from livestock effluents using the method of adsorption. In this study, the effects of DOM on adsorption behaviors of Cu(II) by Aliinostoc sp. YYLX235, a epiphytic cyanobacterium, were investigated. The results showed that Aliinostoc could effectively bind with Cu(II) and remove it from water. Rather than absorption, most of Cu(II) were bound on the cell surface through adsorption. The decay of Aliinostoc did not resulted in rapid release of Cu(II) into water. The amount of Cu(II) adsorbed by Aliinostoc through ion exchange and complexation was decreased by DOM addition.

Improvement surfactin production by substitution of promoters in Bacillus subtilis TD7

Surfactin is one of the most representative biosurfactants and exhibits excellent surface activity plus other biological effects. It has potential applications in microbial enhanced oil recovery, environmental bioremediation, agricultural bio-control, pharmacy, cosmetics and food industries. The low yield of the surfactant from wild strains is a key restriction for industrial applications. The construction of genetically engineered bacteria by promoter substitution is an effective method to enhance surfactin production, as the promoter is a key element in gene expression. This study focuses on constructing strains with efficient surfactin production by replacing the native srfA promoter by strong promoters. In this study, two different promoter patterns with different homology arm positions were used for srfA promoter substitution. The most efficient installation way was identified as the sequence between the transcriptions start site and ribosome binding site of srfA. Moreover, eight endogenous strong auto-inducible phase-dependent promoters were chosen to substitute the native promoter of srfA using an effective substitution by the CRISPR-Cas9 system. As a result, high surfactin yielding strains with potential application in industry were constructed. According to the results, three constructed strains with promoters P43, PspoVG, and PyvyD showed increased yields of 3.5, 2.8, and 2.3 times over the wild stain B. subtilis TD7.

Degradability and Biochemical Pathways of the Endocrine-disrupting Plasticizers Phthalate Esters in Plastics by Microorganisms

Phthalate esters (PAEs) are a group of endocrine-disrupting organic chemicals commonly used as additives in the manufacturing of a wide range of plastics. Large quantities of different phthalate esters have been used in specific products for quality and performance by the manufacturing industries, and they pose a significant risk to human health and the ecological quality of the environments due to leaching out of phthalates from plastic products and their high mobility. Since phthalate esters are most removed efficiently through biodegradation by microorganisms in the environments, it is important to understand the efficiency, microorganisms involved, biochemical transformation processes and mechanisms of phthalate metabolism by the specific microorganisms. This article addresses the degradation of endocrine-disrupting phthalates and their fates by an integrative comparison and analysis on efficient PAEs-degrading microorganisms, the microbial metabolism, and the biochemical processes and limitation. The comparison reveals that no significant difference is evident on efficiencies between single strains of bacteria or the mixed bacterial consortia when degradation can be carried out. However, there are a few important characteristics among the efficiencies of the PAEs-degrading bacteria. The microorganisms shall utilize the specific phthalate ester as the sole source of carbon and energy. They shall mineralize the substrates, including the original compound and its degradation intermediates to achieve a complete removal. In addition, it is of practical importance for the bacteria to adapt and survive in a range of temperatures, salinity and pH as well as in the presence of indigenous microorganisms in bioremediation of contaminated sites or wastewater treatment. This review also reveals that caution should be given to both the presentation and interpretation of the degradation results for a comprehensive knowledge, particularly data on bacterial growth, extraction and analysis of residual PAEs, and the confounding use of surfactants or co-substrate in the research. The public awareness of plasticizers as an environmental pollutant is mostly due to its increasing quantities being used, constant contacts with human population on a daily basis and potential health hazards. Its toxicity shall be address more focused on reproductive biology meaningfully than the traditional mortality test in toxicology for the significant effects on animals including human.

Biodegradability of Synthetic Plastics and Polymeric Materials: An Illusion or Reality in Waste Managements?

Petroleum-based plastics are an indispensable part of our daily life now because they are flexible, convenient, light weight, waterproof, and also have good mechanical strength and economical. They are especially suitable in products packaging, but they accumulate in soils, rivers and oceans, resulting in undesirable environmental and ecological hazards. Conventional plastics wastes in landfills occupy a much higher proportion of space because of their light-weight and extremely low biodegradation rate under anaerobic conditions. Composting is a treatment process to deal with biodegradable plastics (BPs) wastes and diverts a fraction of the wastes from landfilling to provide a feasible solution to the waste management problem. Biodegradability and degradation rate of plastics products depend on the fundamental chemical characteristics of the specific plastics mainly while environmental conditions and the establishment of an active degrading population of microorganisms contribute to a small extent of the fate of plastics after disposal. As the biodegradation rate varies among different plastics, a group of testing methods are available for assessing the degradability of different plastics and their products. Plasticizers in plastics and polymeric materials deserve a special attention up on their dispersal and ecological impact because of their endocrine-disrupting activity. The widely used phthalate esters are biodegradable by indigenous microorganisms in the environments, but the large quantity of them used is a serious issue to the environment and ecological health. However, there is an apparent cost difference between biodegradable and synthetic plastics, which hinder the commercialization of biodegradable ones for daily use. Separation of waste collection and education can contribute to the plastic waste management. It is unrealistic that biodegradable plastics are the solution to the problems facing today’s society on waste management. The ultimate goal is to reduce the use by society members so that amount of waste generated can be reduced so that waste products can be reduced from the sources.

Biodegradation of Phenol by Bacillus simplex: Characterization and Kinetics Study

Phenol is one of the main pollutants that have a serious impact on the environment and can even be very critical to human health. The biodegradation of phenol can be considered an increasingly important pollution control process. In this study, the degradation of phenol by Bacillus simplex was investigated for the first time under different growth conditions. Six different initial concentrations of phenol were used as the primary substrate. Culture conditions had an important effect on these cells' ability to biodegrade phenol. The best growth of this organism and its highest biodegradation level of phenol were noticed at pH 7, temperature 28 °C, and periods of 36 and 96 h, respectively. The GC-MS analysis of the bacterial culture sample revealed that further degradation of the catechol by 1,2-dioxygenase produce a cis, cis-mucconic acid via ortho-pathway and/or by 2,3-dioxygenase into 2-hydroxymucconic semialdehyde via meta-pathway. The highest biodegradation rate was perceived at 700 mg/L initial phenol concentration. Approximately 90% of the phenol (700 mg / L) was removed in less than 96 hours of incubation time. It was found that the Haldane model best fitted the relationship between the specific growth rate and the initial phenol concentration, whereas the phenol biodegradation profiles with time could be adequately described by the modified Gompertz model. The obtained parameters from the Haldane equation are: 1.05 h−1, 9.14 ppm, and 329 ppm for Haldane's maximum specific growth rate, the half-saturation coefficient, and the Haldane’s growth kinetics inhibition coefficient, respectively. The Haldane equation fitted the experimental data by minimizing the sum of squared error (SSR) to 1.36 X 10-3.

Comparative response of SOD at molecular level in different plants against cadmium and drought stress

Abiotic stress like drought and heavy metal imposes a negative impact on exposed plants’ growth and development, commences over production of reactive oxygen species (ROS) inside plant cells resulting in oxidative stress at the cellular level. After that, plants activate multiple defense mechanisms, within which the superoxide dismutase (SOD) family acts as the first line of defense to eliminate ROS. From the literature, it is evident that fewer studies have been carried out in combination with molecular evolution and phylogenetics, and expression profile of the SOD genes amidst dicot and the monocot at subcellular level against drought stress and cadmium (Cd) metal exposure. In the present study, SOD isogenes are identified in purposely elected two dicot plants i.e. Arabidopsis thaliana (9 genes), Solanum lycopersicum (8 genes) and two monocot plants namely Triticum aestivum (11 genes), and Oryza sativa (7 genes), respectively. Based on the amino acids sequence similarities, the identified proteins are classified into three subfamilies in accordance to their phylogenetic relationships, namely Cu/ZnSOD, FeSOD, and MnSOD. High variability observed between Cu/ZnSOD with other two groups i.e. FeSOD and MnSOD which showed lesser variation within them by using secondary structure predication. Subcellular localization suggested that genes encoding FeSOD, MnSOD and Cu/ZnSOD are predominant in chloroplasts, mitochondria, and cytoplasm, respectively in studied plants. The expression profiling through microarray analysis showed varied strategies of SOD isogenes against drought stress and Cd exposure individually. From the perspective of evolution, this study would expand our knowledge for vividly understanding the role of distinctive SOD isogenes in detoxifying ROS in different plants under various abiotic stresses.