The effects of media temperature, agitation rate and molasses concentration on the yield of fermentation in xanthan gum production process were investigated. Xanthan gum was produced in batch fermentation by Xanthomonas campestris PTCC 1473 from molasses. At 32 °C, 500 rpm and media with 30 g/l of total sugar, maximum production of xanthan gum (17.1 g/l) was achieved. For the purity of the xanthan FTIR spectrum was obtained. The identified spectrum was compared with the commercial product. In batch culture, several kinetic models for the biochemical reactions were extensively studied. The growth kinetic parameters were evaluated by unstructured model and derived from the related equations. Based on Malthus and Logistic rate equations, the maximum specific growth rate, μ max , and initial cell dry weight, X 0 , were defined. Luedeking-Piret and Modified Luedeking-Piret models were applied for the product formation and substrate consumption rates. In batch experiments, the kinetic parameters for the growth associated (m, a) and non-growth associated (n, b) parameters were determined.

S-naproxen by enantioselective hydrolysis of racemic naproxen methyl ester was produced using immobilized lipase. The lipase enzyme was immobilized on chitosan beads, activated chitosan beads by glutaraldehyde, and Amberlite XAD7. In order to find an appropriate support for the hydrolysis reaction of racemic naproxen methyl ester, the conversion and enantioselectivity for all carriers were compared. In addition, effects of the volumetric ratio of two phases in different organic solvents, addition of cosolvent and surfactant, optimum pH and temperature, reusability, and inhibitory effect of methanol were investigated. The optimum volumetric ratio of two phases was defined as 3:2 of aqueous phase to organic phase. Various water miscible and water immiscible solvents were examined. Finally, isooctane was chosen as an organic solvent, while 2-ethoxyethanol was added as a cosolvent in the organic phase of the reaction mixture. The optimum reaction conditions were determined to be 35 °C, pH 7, and 24 h. Addition of Tween-80 in the organic phase increased the accessibility of immobilized enzyme to the reactant. The optimum organic phase compositions using a volumetric ratio of 2-ethoxyethanol, isooctane and Tween-80 were 3:7 and 0.1% (v/v/v), respectively. The best conversion and enantioselectivity of immobilized enzyme using chitosan beads activated by glutaraldehyde were 0.45 and 185, respectively.

Tetracycline is one of the most widely used antibiotics that causes contamination of aqueous environments and has raised serious concern during the past few years. In this work, adsorption of tetracycline on a modified zeolite was studied through a batch system. Synthetic zeolite 13X was modified using Fe(III). The results show that the removal efficiency of tetracycline by modified zeolite has considerably increased. Different experiments were carried out in order to analyze the effect of parameters such as pH, initial concentration of tetracycline, time, etc. The results indicate that tetracycline adsorption on the zeolite strongly depends on the pH of the solution due to amphoteric functional groups of tetracycline and maximum adsorption capacity of tetracycline by modified zeolite with a pH of approximately 6. The Langmuir isotherm shows good agreement with the experimental data suggesting monolayer adsorption. Maximum adsorption capacity of the modified zeolite reached at the experiments is almost 200 mg/g. XRD, XRF and FTIR results confirm the existence of the Fe phase in the zeolite texture. Amide groups of TC were responsible for the complexation with Fe 3+. Also, tetracycline removal was studied in a continuous column to simulate an industrial waste water process.

Recently due to strict environmental regulations, concentration of hazardous organic sulfur compounds from gas stream should be reduced. A new efficient method for removal of hydrogen sulfide from natural gas is required. Conventional methods for desulfurization are very costly and required solvent, high operation temperature, and pressure. In contrary, biological processes have great potential to eliminate hydrogen sulfide under mild conditions. Extensive research has been conducted on sulphur oxidizing bacteria for the removal of hydrogen sulfide. However, with present achievements is still not enough to satisfy the industrial requirements. To improve the biodesulfurization efficiency additional research required to isolate a particular strain organism. In this article the ability of newly isolated bacteria was discussed. For this purpose the mixed culture was isolated from native hot spring in the hill side of Damavand Mountain (in North of Iran). The isolated culture was inoculated on nutrient plate agar under anaerobic condition. After incubation for duration 72 h two distinct colonies white and yellow color were observed. Each species was separately grown in nutrient broth and then the optimal conditions were obtained. The desired conditions for white colony such as temperature, pH and agitation rate were 36˚C, 6.5 and 180 rpm, respectively. All the above conditions for yellow colony were identical except for pH slightly reduced to 6. On the basis of optimal biodesulfurization conditions, maximum cell dry weight for the each isolated specie was achieved; approximately were 1.35 and 1.12 g.l -1 for white and yellow colony respectively. The removal of hydrogen sulfide from natural gas stream as the aim of present work was obtained. The percentage removals were 67 and 35% for white and yellow colony, respectively.

Biodegradation of ethyl acetate in batch and continuous cultures was investigated. Pseudomonas putida was selected as a biological agent to biodegrade ethyl acetate. In batch experiment, biodegradation of ethyl acetate was performed in the range of 25-35°C. Walnut shells treated with alkaline solution as natural packing materials provided an appropriate environment for the growth and immobilization of microorganisms. The active biofilm was fully established on the surface of natural packing material. In the early stage, experiments were performed at Empty Bed Resistance Time (EBRT) of 60 s. Maximum removal efficiency of 99% was achieved at inlet concentrations lower than 430 ppm of ethyl acetate. The removal efficiency dropped to 80% with an increase of inlet concentration of ethyl acetate. In order to enhance the removal efficiency, the EBRT was increased from 60 to 75 s. At EBRT of 75 s, the removal efficiency was maintained above 80% even though the inlet concentration increased to 5150 ppm. Michaelis-Menten and Logistic models were perfectly fitted to experimental data. In addition, the kinetic parameters of presented models were defined.