Vol 2, No 2 (2017)

Table of Contents

Biodegradation and Transformation

771 Views, 462 PDF Downloads
Karen Choi Yuen Yip, Guo-Xia Zhang, Ji-Dong Gu


Aerobic biodegradation and metabolite identification of indole by the Pseudomonas putida strain mpky-1 isolated from coastal sediment of the Inner Deep Bay of Hong Kong was investigated in this study. This strain had 99.1% similarity with P. putida known. The biochemical degradation pathway of indole involved an initial hydroxylation reaction at the C-2 position to form oxindole followed by a second hydroxylation at the C-3 position to isatin prior to the cleavage of the 5-member carbon ring. This bacterium grew better at 22oC though it was capable of growth at low temperature (15oC in this study) with a longer lag phase. Both the bacterial specific growth rate and the biodegradation rate increased from 0.0035/hr to 0.0249/hr and from 15oC to 30oC, respectively. P. putida mpky-1 grew quicker at pH 6.4 (specific growth rate, 0.0115/hr) than pH 7.4 (specific growth rate, 0.0066/hr) and pH 8.4 (specific growth rate, 0.036/hr) although the lag time of bacterial growth at pH 7.4 and pH 8.4 (15.01 hr and 15.00 hr, respectively) was very similar. The decrease in bacterial growth rate was observed when salinity increased from 5‰ to 30‰. P. putida mpky-1 may adapt to the Mai Po and Inner Deep Bay and degrade indole due to the polluted condition.

1370 Views, 388 PDF Downloads
Shuai Liu, Jia-Jie Hu, Jia-Xian Shen, Shu Chen, Guang-Ming Tian, Ping Zheng, Li-Ping Lou, Fang Ma, Bao-Lan Hu


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.

1004 Views, 400 PDF Downloads
Zhi-Qiang Xiong, Guo-Xing Wang, Zhao-Chen Huo, Lei Yan, Ya-Mei Gao, Yan-Jie Wang, Ji-Dong Gu, Wei-Dong Wang


Composting is a controlled biological process used to stabilize and transform waste into a soil treatment. Aeration rate is one factor that controls the process of composting, as it ensures the growth of adequate aerobic microbe populations. To investigate the effect of aeration rates on the physicochemical indexes of compost and the loss of nitrogen content during composting, aerobic composting  processes with different aeration rates (A: 0.2 L/min/kg TS, B: 0.05 L/min/kg TS and C: 0 L/min/kg TS) were studied. Ammonium-nitrogen, nitrate nitrogen, total nitrogen and other factors in compost samples from different periods were measured. The results showed that aeration rate significantly affected O2 content under different conditions. The aeration rate also significantly affected water content, nitrate nitrogen, and nitrogen loss. NH3 emissions increased as aeration rates increased at high temperatures owing to nitrogen loss. These results showed that aeration rate had a significant effect on total nitrogen and ammonia emissions (p<0.05). Thus, optimization of the ventilation method could significantly increase seed germination rate.

678 Views, 140 PDF Downloads
Guo-Xia Zhang, Ji-Dong Gu


Degradability of syndiotactic poly ([R]-β-hydroxybutyrate) (syn-PHB), a chemically synthesized PHB, was investigated in this study by incubation of the 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 a random cleavage of the 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.


Microbial Dynamics

703 Views, 331 PDF Downloads
Ji-Dong Gu, William B McGill


Microbial biomass C and N dynamics was studied of the soils cropped to faba bean, canola, barley and summer fallow in the Breton Plots in Canada. Stable isotope 15N was used to trace the incorporation of 15N into microbial biomass fraction. Flush N was calculated in three ways to compare discrepancies that may exist in results widely published. Crop and cropping had significant effects on microbial biomass C and respiration C of treated soils. Microbial biomass C estimated in faba bean plots was higher than that in canola, barley or summer fallow by 44, 39 and 167% on the average of four samplings. A peak was observed for canola, barley and summer fallow around July 24, but it was not evident for faba bean. Flush N was not significant upon treatments, and 15N incorporated into the flush N fraction and 15N excess varied with treatments. Among three approaches of calculating flush N, we found that NH4+ in fumigated less the nonfumigated soils yielded the best results, NH4+ in fumigated without control resulting in deviation from considering a control by 1-2% in faba bean, 1-6% in barley and 1% in canola and summer fallow.



740 Views, 207 PDF Downloads
Xiao Zhuo, Jie Wei, Jian-Feng Xu, Ru-Tan Pan, Gang Zhang, Yun-Long Guo, Xiao-Ying Dong, Ling Long, Yongfeng Li


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.


Plastics and Biodegradability

1587 Views, 539 PDF Downloads
Ji-Dong Gu


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.



627 Views, 175 PDF Downloads
Xiao-Zhang Yu, Fei-Fei Zhang


Responses of phenolic compounds were 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.


Cookies Notification