The presence of toxic compounds like toluene has caused extensive contamination in oil-contaminated environments. Using bacteria to degrade monoaromatic compounds could be a good approach to finding a suitable bioaugmentation agent. In this study on toluene, degrading bacterial species were isolated from oil-contaminated environments (located in Bandar-Anzali, Guilan, Iran). The strain has been molecularly identified as Bacillus cereus ATHH39 (Accession number: KX344721) by partial sequencing of the 16S rDNA gene. Response surface methodology (RSM) was used for biodegradation of toluene by ATHH39 by implementing the central composite design (CCD). The central composite design (CCD) was applied to optimize and investigate pH, temperature, and toluene concentrations and their interactions for enhancing cell growth and toluene degradation by ATHH39 under in vitro conditions. The variables (pH, temperature, and toluene concentrations) with the highest significant impacts on growth and toluene degradation were selected. According to the prediction and optimization function of the design expert software, the optimum conditions of cell growth and toluene degradation were found. When pH, temperature, and toluene concentration were adjusted to 6.72, 33.16ºC and 824.15 mg/l, respectively, cell growth and toluene degradation reached OD 600 = 0.69 and 64.11%, respectively, which is very close to the predicted cell growth and toluene degradation of OD 600 = 0.71 and 65.85%, indicating that the response surface methodology optimization of process parameters for cell growth and toluene degradation is reliable. Based on the results, the ATHH39 strain was introduced as a useful microorganism with the potential for bioremediation of wastewater containing toluene.
The release of pharmaceutical wastewaters in the environment is of great concern due to the presence of persistent organic pollutants with toxic effects on environment and human health. Treatment of these wastewaters with microorganisms has gained increasing attention, as they can efficiently biodegrade and remove contaminants from the aqueous environments. In this respect, bacterial immobilization with inorganic nanoparticles provides a number of advantages, in terms of ease of processing, increased concentration of the pollutant in proximity of the cell surface, and long-term reusability. In the present study, MCM-41 mesoporous silica nanoparticles (MSN) were immobilized on a selected bacterial strain to remove alprazolam, a persistent pharmaceutical compound, from contaminated water. First, biodegrading microorganisms were collected from pharmaceutical wastewater, and Pseudomonas stutzeri was isolated as a bacterial strain showing high ability to tolerate and consume alprazolam as the only source for carbon and energy. Then, the ability of MSN-adhered Pseudomonas stutzeri bacteria was assessed to biodegrade alprazolam using quantitative HPLC analysis. The results indicated that after 20 days in optimum conditions, MSN-adhered bacterial cells achieved 96% biodegradation efficiency in comparison to the 87% biodegradation ability of Pseudomonas stutzeri freely suspended cells. Kinetic study showed that the degradation process obeys a first order reaction. In addition, the kinetic constants for the MSN-adhered bacteria were higher than those of the bacteria alone.
The possibility of using treated oil palm empty fruit bunch (OPEFB) fibres as substrate for cellulase production by Aspergillus terreus was studied using shaking flask fermentation. The effect of different chemical pretreatments, i.e. formic acid, acetic acid, propylamine, phosphoric acid, and n-butylamine, on the suitability of OPEFB fibres as fermentation substrate was investigated. The findings revealed that pretreatment with these chemicals significantly (P<0.05) increased the cellulose and reduced the lignin contents prior to enzymatic hydrolysis. However, fermentation using OPEFB fibres pretreated with phosphoric acid gave the highest cellulase production, which was related to high cellulose content. Further improvement in cellulase production was obtained when the chemically pretreated OPEFB fibres were subsequently treated hydrothermally (autoclaved at 160oC for 10 min) and then biologically (using effective microorganisms). The final activity of the three main components of cellulase (FPase, CMCase, and β-glucosidase) obtained in fermentation by A. terreus using optimally treated OPEFB fibres was (0.77 U mL−1, 8.5 U mL-1, and 6.1 U mL-1), respectively. The production of all these three major components of cellulase using pretreated OPEFB fibres (i.e. chemical, hydrothermal, and biological) were about three times higher than those obtained from fermentation using untreated OPEFB fibres.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.