Although the number of human infections decreased, human prevalence increased from 4.9% in 1995 to 5.1% in 2004.

With the sharp increase in population and modernization of society, environmental pollution resulting from petroleum hydrocarbons has increased, resulting in an urgent need for remediation. Petroleum hydrocarbon-degrading bacteria are ubiquitous in nature and can utilize these compounds as sources of carbon and energy. Bacteria displaying such capabilities are often exploited for the bioremediation of petroleum oil-contaminated environments. Recently, microbial remediation technology has developed rapidly and achieved major gains. However, this technology is not omnipotent. It is affected by many environmental factors that hinder its practical application, limiting the large-scale application of the technology. This paper provides an overview of the recent literature referring to the usage of bacteria as biodegraders, discusses barriers regarding the implementation of this microbial technology, and provides suggestions for further developments.

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A fungus, XJ-1, isolated from chicken manure compost was phylogenetically related to Penicillium chrysogenum. The minimum inhibitory concentrations of the fungus for Cd2+, Cu2+, Cr3+, Cr6+, Co2+ and Zn2+ were 300, 85, 55, 8, 25 and 70mM on plates and 200, 65, 30, 2, 30 and 48mM in liquid media, respectively. Biosorption of Cd2+ by XJ-1 was investigated as a function of initial pH, contact time, biomass loading and Cd+ concentration. According to the Langmuir isotherm, the maximum adsorption of Cd2+ was 100.41 mg g(-1) dry biomass. Analyses using FTIR, SEM and XPS showed that the functional groups -OH and -C=O on the XJ-1 cell wall are the dominant binding sites for Cd2+. The results indicate that XJ-1 biomass is an efficient biosorbent for Cd2+ and has great potential for the in situ remediation of environments contaminated with heavy metals.

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The filamentous fungi XLA and XLC isolated from Cd-contaminated soil were identified morphologically and phylogenetically as Paecilomyces lilacinus and Mucoromycote sp., respectively. The minimum inhibitory concentrations (MICs) of Cd2+, Co2+, Cu2+, Zn2+, Cr3+ and Cr6+ in minimum mineral (MM) medium agar plates were 29,786, 2945, 9425, 5080, 1785 and 204 mg·L−1 for XLA and 11,240, 884, 9100, 2540, 3060 and 51 mg·L−1 for XLC, respectively. Favorable biosorption conditions for adsorption of Cd2+ by the tested fungi were investigated. Efficient performances of the biosorbents were described using Langmuir isotherm model, and the predicted maximum biosorption capacities for Cd2+ were 77.61 mg·g−1 of XLA and 79.67 mg·g−1of XLC. Experiments on desorption potential of biosorbents validated their efficacy at a large scale. Results showed that XLA obtained a desorption rate of 84.7% by 2% EDTA and XLC gained a desorption rate of 78.9% by 0.1 M HCl. Analysis by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and X-ray photoelectron spectroscopy (XPS) suggested that groups of C–N, COO– for XLA and C–N, CH2 and phosphate for XLC were the dominant binding sites for Cd2+ biosorption. Our results indicated that the fungus XLA, rather than XLC, could potentially be used as an inexpensive, eco-friendly and effective bioremediation agent for the removal of Cd2+ from wastewater.