Sharif Digital Repository

In this study ethanol was produced without using expensive commercial enzymes from sugarcane bagasse. Alkali pretreatment was used to prepare biomass before enzymatic hydrolysis. The comparison between NaOH, KOH and Ca(OH)2 revealed that NaOH has been more effective on bagasse structure. The required enzymes for biomass hydrolysis were produced by bagasse solid state fermentation using three fungi: Trichoderma longibrachiatum, T. reesei and Aspergillus niger. Results indicated enzyme solution produced by A. niger has functioned better than the other two in cellulose conversion during sole hydrolysis. Ethanol was produced by simultaneous saccharification and fermentation (SSF) with on-site... 

The budding yeast Saccharomyces cerevisiae is the first eukaryote whose genome has been completely sequenced. It is also the first eukaryotic cell whose proteome (the set of all proteins) and interactome (the network of all mutual interactions between proteins) has been analyzed. In this paper we study the structure of the yeast protein complex network in which weighted edges between complexes represent the number of shared proteins. It is found that the network of protein complexes is a small world network with scale free behavior for many of its distributions. However we find that there are no strong correlations between the weights and degrees of neighboring complexes. To reveal... 

The purpose of this study was to investigate the use of a horizontal packed bed bioreactor, named Biopack, to treat high strength wastewater, such as bakers yeast wastewater. The Biopack system (RBCP) is a modified rotating biological contactor and the system was applied for secondary treatment. The RBCP system produced high treatment efficiencies, COD removal was 94.9% when COD was 472 mg/l and surface organic loading = 0.187 kg COD/m2 per day and surface hydraulic loading = 6 l/m2 per day. Variations of surface hydraulic loading from 6 to 11.9 l/m2 per day produced a decrease in COD removal efficiency from 94.9 to 58.6%. Other factors, such as shock load, retention time and rotational... 

This paper discusses the studies carried out for the optimal production of enzyme l-asparaginase (l-asparagine amidohydrolase, EC 3.5.1.1) from Escherichia coli (ATCC 11303). It was found that inoculum age of 18 h and inoculum size of 10% were the most favorable operating conditions for enzyme production. Lactose, yeast extract and KH 2PO 4 were found to be the best carbon, nitrogen and ion sources, respectively. Statistical method was used to survey how various medium conditions affect the enzyme production. By response surface methodology, the values of lactose, tryptone, yeast extract, KH 2PO 4 and l-asparagine concentration were investigated to obtain the maximum enzyme activity. The... 

Applying engineering approaches to non-engineering systems such as biological systems has brought a new research filed to the surface. The sole purpose of this research is mathematical modeling the cell cycle control system in the fissionyeast cell using Ordinary Differential Equations (ODE).This paper, in fact, introduces the capabilities of engineering knowledge and engineering of control, in particular, in this field. ©2009 IEEE  

Azo dye degradation in wastewater treatment is a subject which has garnered the attention of many research studies. In this study, an innovative approach, namely, an integrated system of five batches (ISFB), was developed to investigate the capability of Saccharomyces cerevisiae ATCC 9763 for continuous degradation of methyl red as a representative azo dye. Toward this end, an expanded immobilized microbial bed (EIMB) reactor was established with a bed of encapsulated yeast cells in sodium alginate. EIMB reactor was run in two modes, single batch and ISFB. Moreover, durability of the microbial cells was evaluated by repeating the continuous decolourization eight sequential times in EIMB at... 

Gas sparging and back-flushing treatments were compared as a means to tackle the problem of fouling in yeast microfiltration. Based on the feed and membrane characteristics, it was shown that either of these techniques could be superior to the other in order to overcome the problem. At more concentrated feed streams the main cause of flux decline was cake formation. In this condition gas sparging showed greater efficiency in flux enhancement. On the other hand at lower feed concentration the relative importance of internal fouling due to pore blockage, increased. In this case back-flushing was more effective. © 2007  

The bioconversion of abundant and renewable cellulosic biomass into ethanol as an alternative to petroleum is gaining importance due to the realization of diminishing natural oil and gas resources. Agricultural and foresty plant residues are an abundant and renewable source of sugar substrates that could be fermented to ethanol. A thermochemical treatment of biomass in which both cellulose and hemicellulose are hydrolyzed to soluble sugar is necessary before yeast fermentation. After thermochemical treatment, cellulase enzymes must be introduced in the system to hydrolyze any remaining cellulose. The simultaneous saccharification and fermentation (SSF), is a method which converts... 

The present work was aimed to account a green and eco-friendly synthesis of palladium nanoparticles using Rosmarinus officinalis leaves extracts for the first time, therefore, that can be an acceptable replacement for chemical media to improve potential biological properties. The synthesized palladium nanoparticles were fully characterized using FT-IR, XRD, FESEM, TEM and UV/Vis spectroscopy techniques. Catalytic activity was investigated by Mizoroki-Heck reaction, and optimized based on solvent, temperature and time of the reaction, and the best results were found in water as a green media without any additional reagents. Biological activity of the synthesized nanoparticles were evaluated... 

The production of protease by Bacillus licheniformis BBRC 100053 was studied. The most appropriate medium for the growth and protease production is composed of: lactose 1 %, yeast extract 0.5 %, peptone 0.5 %, KH 2PO4 0.1%, MgSO4.7H2O 0.02 %. Enzyme production corresponded with growth and reached a maximums level (589 U/ml) during the stationary phase at 35 °C, pH equivalent to 10 and with 150 rpm after 73 hours. Protease activity was highest at pH 8 and 45 °C. The best carbon sources are respectively lactose and maltose and the best nitrogen source is peptone The protease was highly active and stable from pH 7.0 to 11.0 with an optimum at pH 7-8.Thermo stability of the enzyme was considered... 

The production of protease by Bacillus licheniformis BBRC 100053 was studied. The most appropriate medium for the growth and protease production is composed of: lactose 1%, yeast extract 0.5%, peptone 0.5%, KH2PO 4 0.1%, MgSO4.7H2O 0.02%. Enzyme production corresponded with growth and reached a maximums level (589 U/ml) during the stationary phase at 35°C, pH equivalent to 10 and with 150 rpm after 73 hours. Protease activity was highest at pH 8 and 45°C. The best carbon sources are respectively lactose and maltose and the best nitrogen source is peptone. The protease was highly active and stable from pH 7.0 to 11.0 with an optimum at pH 7-8.... 

Dielectrophoresis is a robust approach for manipulating bioparticles in microfluidic devices. In recent years, many groups have developed dielectrophoresis-based microfluidic systems for separation and concentration of various types of bioparticles, where the gradient of the electric field causes dielectrophoresis force acting on the suspended particles. Enhancing the gradient of the electric field with three-dimensional (3D) electrodes can significantly improve the efficiency of the system. Implementing planar electrodes in a 3D arrangement is a simple option to form a 3D-electrode configuration. This paper reports the development of a novel dielectrophoretic microfluidic system for... 

Statistically based experimental designs were applied to screen and optimize the bioleaching of spent hydrocracking catalyst by Penicillium simplicissimum. Eleven factors were examined for their significance on bioleaching using a Plackett-Burman factorial design. Four significant variables (pulp density, sucrose, NaNO3, and yeast extract concentrations) were selected for the optimization studies. The combined effect of these variables on metal bioleaching was studied using a central composite design (CCD). Second-order polynomials were established to identify the relationship between the recovery percent of the metals and the four significant variables. The optimal values of the variables... 

Paenibacillus polymyxa ATCC 21830 was used for the production of curdlan gum for first time. A Box-Behnken experimental design was applied to optimize six variables of batch fermentation culture each at three levels. Statistical analyses were employed to investigate the direct and interactive effects of variables on curdlan production. Optimum cultural conditions were temperature (50. °C), pH (7), fermentation time (96. h), glucose (100. g/L), yeast extract (3. g/L) and agitation speed (150. rpm). The yield of curdlan production was 6.89. g/L at optimum condition medium. Response surface methodology (RSM) and artificial neural network (ANN) were used to model cultural conditions of curdlan... 

Rhamnolipids (RLs) produced by the opportunistic human pathogen Pseudomonas aeruginosa are considered as potential candidates for the next generation of surfactants. Large-scale production of RLs depends on progress in strain engineering, medium design, operating strategies, and purification procedures. In this work, the rhlAB genes extracted from a mono-RLs-producing strain of P. aeruginosa (ATCC 9027) were introduced to an appropriate safety host Pseudomonas putida KT2440. The capability of the recombinant strain was evaluated in various media. As a prerequisite for optimal medium design, a set of 32 experiments was performed in two steps for screening a number of macro-nutritional... 

Pichia pastoris is used extensively as a production platform for many recombinant proteins. The dissolved oxygen (DO) is one of the most important factors influencing protein production. The influence of the DO on productivity has not been studied independent from the feed rate. In this work, various DO levels were investigated independent from the feed rate. The model system was recombinant P. pastoris under the control of methanol-induced alcohol oxidase promoter, which expressed HRP as the target protein. No significant effect was observed in terms of titer and specific productivity, which is a confirmation of the fact that the DO in a one-compartment system cannot boost productivity for...