Vol 6, No 1 (2021)

Table of Contents

Research Articles

191 Views, 26 PDF Downloads
Mohammad A. Alkafaween, Hamid Ali Nagi Al-Jamal, Khaled M Khleifat, Haitham Qaralleh, Muhamad O. Al-limoun, Moath Alqaraleh, Abd Elalim Abu Sabha, Khalid A. Shadid, Khalid Alqaisi, Rula Al Buqain, Nida Karameh, Malik Amonov, Anas Abed
DOI:10.26789/AEB.2021.01.005

Abstract

Introduction: Fungi are one of the main approaches for synthesis of metallic nanoparticles (NPs), which can have medical and biotechnological applications such as their role in anti-bacterial, anti-cancer and various industrial activities. Objective: The current research focused on the biosynthesis of silver nanoparticles (AgNPs) using airborne fungi isolated from Al-karak general hospital operation rooms. Materials and Methods: The fungal isolate was identified at the species level by sequencing ITS as Aspergillus flavus. The confirmation and characterization of biosynthesized AgNPs were conducted using UV-Vis spectrophotometer, Zeta potential, Zeta sizer, FT-IR, XRD and transmission electron microscope (TEM) analyses. Results: The average diameter of the resulting AgNPs was 499.3 nm with a PDI value of 0.28. The zeta potential was -34.9 mV which reflects the ability of these nanoparticles to have a sufficient charge, because it is electrostatically stable and therefore resists self-assembly. TEM revealed that these biosynthesized AgNPs were regular and spherical in shape. The images of TEM showed that the size of AgNPs were smaller than those that were observed by DLS examination due the drying process that caused particle shrinkage. The average size of AgNPs were less than 40 nm. AgNPs exhibit different minimal inhibitory concentrations (MIC) against seven different bacteria (K. pneumonia, E. coli, E. cloacae, S. aureus, S. epidermidis, and Shigella sp.). The MICs ranged between 0.025 and 0.075 mg/mL with P. aeruginosa an exception which was the most resistant one, showing its MIC as   ˃ 0.125 mg/mL. Discussion and Conclusion: The results indicate that these molecules can be used as an important source for the treatment of many diseases caused by bacteria, in addition to testing these molecules in various fields such as cancer treatment and even in various biotechnological applications.

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428 Views, 119 PDF Downloads
Bo-Zhong Mu, Fang-Fang Liu, Yi-Fan Liu, Yi-Wei Qiao, Yu-Zhe Guo, Fang-Yue Kuang, Xiu-Qing Lin, Jiang Ye, Jin-Feng Liu, Shi-Zhong Yang, Hui-Zhan Zhang, Wolfgang Sand
DOI:10.26789/AEB.2021.01.004

Abstract

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.

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31-41
624 Views, 171 PDF Downloads
Manasa V Anand, R Ravishankar, Kiran S Vasist, Madhu H N
DOI:10.26789/AEB.2021.01.002

Abstract

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.

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6-15

Review

697 Views, 197 PDF Downloads
Ji-Dong Gu, Tsz Ching Mak
DOI:10.26789/AEB.2021.01.003

Abstract

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.

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16-30

Commentary

602 Views, 194 PDF Downloads
Ji-Dong Gu
DOI:10.26789/AEB.2021.01.001

Abstract

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.

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