Vol 3, No 1 (2018)

Table of Contents

Biodegradation and Transformation

1268 Views, 215 PDF Downloads
Yong-Yan Niu, Khan Aman, Zheng-Jun Chen, Shuai Zhao, Ke-Jia Wu, Xing-Peng Xiao, Xiang-Kai Li


In this study, a sediment microbial fuel cell (SMFC) system for the simultaneous biodegradation of organic matter and detoxification of hexavalent chromium Cr (VI) was investigated. The total organic carbon (TOC) removal rate of the SMFC with Cr (VI) was 30.07%, which was significantly higher than that in a SMFC without Cr (VI) (13.74%). In the SMFC with Cr (VI), the maximum values of open-circuit voltage (OCV) and power density were 408 mV and 4.8 mW/m2, respectively. During the long-term operation of the SMFC with Cr (VI), 25 mg/L of Cr (VI) were completely reduced from all four consecutive batches over 48 days. MiSeq sequencing revealed that the biofilm microbial community of the anode comprised of Bacteroidetes (42.9%), Proteobacteria (33.6%), Chloroflexi (7.5%), and Euryarchaeota (7.5%) as the predominant phyla. Compared with that of the sediment, certain families were enriched; they included Pseudomonadaceae (46.88-fold), Flavobacteriaceae (5.05-fold), and Syntrophaceae (4.48-fold), which are organic matter-degrading bacteria. These results suggest that SMFCs are useful for TOC removal and detoxification of heavy metals in remediation of contaminated lakes.

830 Views, 371 PDF Downloads
Wing-Yee Au, Xiao-Zhang Yu, Ji-Dong Gu


This paper reviewed the physical and chemical properties of cyanide species - free cyanide and iron-cyanide complexes, and the potential of cyanide phytoremediation with reference to the phytotoxicity of free cyanide and iron-cyanide complexes in plants. There are three possible pathways, which are β-cyanoalanine synthase, sulfur transferase and formamide hydrolase pathways, for transforming and assimilating endogenous free cyanide in plants. Iron-cyanide complexes are generally resistant to microbial and fungal degradation. It is suggested that there may be undiscovered degradation pathways involved in assimilating iron-cyanide complexes in plants; however the detailed pathways of assimilation of iron-cyanides are still unknown. While uptake of free cyanide is mainly by simple diffusion, as iron-cyanide complexes are membrane-impermeable, it is suggested that the complexes may be transported into the plants through the mode of protein mediated uptake. Upon uptake, biological fates of cyanide species vary with different species of cyanide, depending on their chemical properties and concentrations. Phytotoxicity of free cyanide in plants is much higher than that of iron-cyanide complexes as plants could generally withstand a higher concentration of iron-cyanide complexes comparing with free cyanide. However, it is still unsure if the iron-cyanide complexes are toxic themselves or if they disrupt the metabolism of plants indirectly. It is known that endogenous cyanogenic compounds play a role in providing sources of nitrogen and acting as precursors in some biochemical processes in plants. Studies suggested that exogenous cyanide species, to a certain extent, could benefit the plants through providing nutrition to them. However, there is still no study conclusively indicates that there is a direct acquisition of exogenous cyanide species by plants as their alternative source of nitrogen. Further investigations on the degradation pathways of iron-cyanide complexes and the essential enzymes involved in phyto-assimilation of iron-cyanide complexes are required for better understanding of the degradation and assimilation pathways of cyanogenic compounds in plants.

826 Views, 285 PDF Downloads
Xiao-Zhang Yu, Chun-Jiao Lu, Yu-Xi Feng


Chemical forms of chromium (Cr) in rice seedlings (Oryza sativa L. cv. BX139) exposed to either potassium chromate Cr(VI) or chromium nitrate Cr(III) were clarified using a hydroponic study. Seven chemical fractions of Cr in different rice tissues were extracted using a sequential extraction method. Results indicated that exposures to both Cr valents resulted in significant accumulation of Cr in rice tissues and Cr(III) was more bioavailable for rice seedlings than Cr(VI). However, Cr chemical forms were inconsistent in both plant materials (root/shoots) as well as in two different Cr variants. Although both Cr variants caused dose-dependent inhibition on relative growth rates of rice seedlings, different inhibition mechanisms most likely exited using a partial correlation analysis. Both fractions of Cr in cell wall and in intracellular location in roots significantly inhibited the relative growth rates of rice seedlings exposed to Cr(VI), while inhibition of the relative growth rate of rice seedlings exposed to Cr(III) was largely stemmed from Cr partition in intracellular fraction in shoots.


Biotechnology and Applications

680 Views, 244 PDF Downloads
Ji-Dong Gu, William B. McGill


This study was carried out to estimate N-15 allocation into different components of the above- and below-ground plant parts, and to quantify biological N-fixation in faba bean using N-15 dilution method, and both canola and barley as reference crops. Four samplings were conducted during the crop growing season, both above- and below-ground plant parts, and soil were sampled. The above-ground plant was fractionated into leaves, stems, shell, and seeds for faba bean and canola; and dead-leaves, live-leaves, stems, sheaths, husks, and seeds for barley. Roots were extracted from soil by root-washing technique and further separated from dead debris by water floatation and hand-picking. N-15 excess of faba bean above-ground parts was lower than its roots, but the reverse was true for the non-legumes (canola and barley). N-15 fractionation was apparently taking place in various plant parts. Reproductive organs of faba bean had lower N-15 excess than the vegetative ones, but reproductive organs of non-legumes (canola and barley) had higher N-15 excess than the vegetative ones. N-fixation in faba bean was quantified by using N-15 dilution method with either canola or barley as a reference crop, the quantity of N derived from atmospheric fixation was 183-199 kg N/ha/yr in the above-ground parts of faba bean and 18-22 kg N/ha/yr in faba bean roots by September 1, when faba beans were not fully matured. Either canola or barley can be a valid reference crop for N-fixation estimation in N-15 dilution method. Total difference method agreed with N-15 dilution method with less than 10% variation in this study. A peak of N-fixation was observed after faba bean flowering and the rate of N-fixation during this period was 4.0-4.7 kg N /ha/day. This study provides the key inofmration for the quantity of N-fixation from atmosphere in faba bean growing on this soil of Canada.

1022 Views, 338 PDF Downloads
Mei Zhang, Wen-Jing Fan, Jing-Yu Wang, Li-Min Cao


The ability to engineer the yeast Saccharomyces cerevisiae to efficiently convert lignocellulosic biomass to ethanol remains a considerable challenge. Here, we propose a new reprogrammable strategy to optimize the expression level of the xylose isomerase (XI) gene with the induction of mutations in S. cerevisiae to improve efficient ethanol production and productivity. We sought to fine-tune the xylose uptake and catabolism abilities of S. cerevisiae during fermentation by improving efficiency of the xylose transporter, which was fused with four copies of the XI gene under the control of different promoters to obtain recombinant yeast strains. In fermentation experiments, the optimized strain CW9 cultured in yeast extract-peptone (YP) medium containing approximately 65 g/L glucose and 55 g/L xylose produced consistent ethanol yields of 0.45 g/g total sugar in about 72 h, which was close to 90% of the theoretical yield. These promising results indicate that strain CW9 is the best producer of ethanol from mixed sugar when synthetically regulating the xylose assimilation pathway. Overall, this study provides an optimal method to control XI expression levels to find better conditions for enhancing biofuel production.


Commentary and Research Analysis

907 Views, 270 PDF Downloads
Ji-Dong Gu


Many synthetic chemicals are widely used in our daily products and they are in constant contacts with humans through many different routes of exposure. In addition to the toxic environmental pollutants known with diminishing usage, plasticizers, a new class of emerging chemicals, are becoming of human health concerns increasingly. Microbial degradation of plasticizers is generally known, but the toxicity and other effects on human and animals are less well understood, especially in terms of reproductive development and endocrine-disrupting activity. Their major impact to Earth is the large quantities of them used on a daily basis and close contacts with biota of the biosphere. Knowledge of their impact shall be focused more specifically on developmental and endocrine system of animals than mortality in traditional toxicology as an end-point to better assess the threats to the biosphere. New directions on this research topic are presented to advance new knowledge in the future research and development.

730 Views, 311 PDF Downloads
Trang Ngoc Kieu Nguyen, Yuh-Shan Ho


The objective of this writing was to conduct a bibliometric analysis of all plant cell publications during the period from 1992 to 2016 by using the Science Citation Index Expanded (SCI-EXPANDED) in the Clarivate Analytics Web of Science database. Basic analysis includes document types, languages, journals, Web of Science categories, distribution by countries and institutes. Indicators such as total, independent, collaborative, first author, corresponding author, and single author publications were applied to compare publication performances by specific countries and institutions of the top ranking. The G7 dominated most of the high impact publications in plant cell research. The high-ranked contributing institutions were non-universities from France, China, Russia, Spain, and USA. University of Tokyo in Japan was the most productive university single out on the top. Plant cell articles were published mainly in Web of Science of plant sciences. Plant Physiology, Plant Journal, and Plant Cell were the top three productive journals on this subject. In addition, top cited and the high impact articles in recent years were also compared. Distributions of words in title, author keywords, and KeyWords Plus in different periods were used for searching research focuses.


Microbial Biofilms

782 Views, 242 PDF Downloads
Cheung Kuen Wan, Ji-Dong Gu


Microbial biofilm formation on surfaces of materials is important information to better understand the adhesion mechanisms and to prevent bacterial colonization. Atomic force microscopy is a useful tool for examining bacterial biofilms formed on metal surfaces. The objectives of the present study were to evaluate the metal surface properties including roughness for attachment of the bacterium Janthinobacterium lividum isolated from drinking-water catridge and to establish the relationship between surface modification through galvanization and susceptibility to biofilm formation. Four metal coupons used in this study were Al Galvanic 0.3%, 5%, 55% and a pure zinc plate. The results showed that several roughness parameters including autocovariance, Z-range, mean roughness, and maximum height increased with bacterial attachment on the selective metal type surfaces. There was a strong positive correlation between different roughness parameters and the number of bacteria attached on the specific metal types. The highest population number of bacteria was observed on Al Galvanized 55% coupon, which was also the roughest surface among the test coupons with different galvanization treatments. Our data suggest that prevention of bacterial attachment on metal surfaces can be achieved by surface treatment to obtain better morphological characteristics.


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