فهرست مطالب fatemeh tabandeh

Effect of different sources of probiotic and prebiotic on growth performance, carcass characteristics, intestinal microflora, and blood metabolites using 720 Ross 308 commercial male broiler chickens in a 3×3 factorial experiment with three levels of probiotic (without probiotic, probiotic type I and type 2) and three levels of prebiotic (without prebiotic, prebiotic type 1 and type II), in a completely randomized design with nine experimental groups (four replications and 20 birds were studied in each replication. Birds that were fed with diets containing type 2 probiotics had a lower conversion factor (P<0.05). Diets containing prebiotic type 1 as well as diets containing probiotic type II and diets containing probiotic type II and two prebiotics under test reduced serum cholesterol and LDL concentrations (P < 0.05). The effect of the experimental treatments on carcass fat was not significant, but the birds fed diets containing prebiotic type 1 had less abdominal fat (P<0.05). At 21 days old, the population of E. coli in the ileum and ceca of birds that received probiotics, prebiotics, and their combinations decreased (P < 0.05). At 38 days of age, feeding the birds with probiotics and prebiotics and a combination of them reduced the population of E. coli in the ceca and increased lactobacillus in the ileum (P < 0.05). The results of this experiment showed that probiotics or prebiotics assayed in this study have positive effects on the increase of beneficial intestinal bacteria (Acid lactic bacteria), blood biochemical traits, and FCR in broiler chickens.

Age-related Macular Degeneration (AMD) is one of the retinal degenerative diseases associated with some degree of dysfunction and loss of Retinal Pigmented Epithelium (RPE) cells and leads to permanent sight loss. Available treatments only slow down its progression. Applying a scaffold to help RPE cells proliferation and make layers has been proposed as a promising approach to treat this group of diseases. In this study, a fuzzy system was used to optimize the situation of making a scaffold. For better adhesion and proliferation of cells, the polycaprolactone scaffold's surface was modified by alkaline hydrolysis and plasma. Some analyses, such as water uptake and biodegradation rate, were done. Then, differentiated human embryonic stem cells (hESCs) were cultured on several groups of scaffolds. Finally, the viability, proliferation, and morphology of differentiated hESC-RPE cells on all groups of the scaffolds were investigated. The nanofibers' diameter was minimized by optimizing voltage and solution concentration with a fuzzy model for the first time, which obtained 110.5 nm, 18.9 kV, and 0.065 g/mL (w/v), respectively. The immersion time of the scaffold in alkaline solution and solution concentration during surface modification were achieved 4.3 M and 104 minutes, respectively, by response surface methodology. Results of the MTT assay showed that the hydrolyzed group had a high proliferation of cells. Scanning electron microscopy observation of cell morphology after 60 days confirmed this result. In conclusion, our results demonstrate that the hydrolyzed scaffold is a suitable bed for cell proliferation, a good option for AMD treatment.

Bioleaching is a practical method to recover metals from low-grade mineral sulfides. The most frequent bacteria involved in the bioleaching of metals from ores are Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Experimental design is a method through which the optimum activity condition will be obtained, avoiding numerous trials and errors. This study aimed to optimize the bioleaching condition of two indigenous iron- and sulfur-oxidizing bacteria from the Meydouk mine, Iran, and evaluate their function in a semi-pilot operation in pure and mixed cultures. After treatment with sulfuric acid, the bacterial DNA was extracted, and further 16S rRNA was sequenced to characterize the bacterial species. The cultivation condition of these bacteria was optimized using Design-expert (6.1.1 version) software. The copper recovery rate and the differentiation in the ORP rate in the percolation columns were also investigated. These strains were isolated from the Meydouk mine for the first time. 16S rRNA analysis revealed that both bacteria belong to the Acidithiobacillus genus. The factors with the most significant impact on Acidithiobacillus ferrooxidans with their optimum level were temperature=35 °C, pH=2.5, and initial FeSO4 concentration=25 g.L-1. Also, initial sulfur concentration had the most significant impact on Acidithiobacillus thiooxidans with the optimum level of 35 g.L-1. Moreover, the mixed culture determined higher bioleaching efficiency compared with the case of employing the pure cultures. Utilizing a mixture of both bacteria, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans elevated the Cu recovery rate due to the synergetic function of the strains. Also, introducing an initial dosage of sulfur and pre-acidification could elevate metal recovery efficiency.

During the manufacture and storage of probiotic products, there are always possibilities that probiotics be exposed to harmful stresses such as high temperature, low pH, various osmotic pressures and high oxygen levels, which can decrease the number of living cells. Encapsulation is one of the methods used to protect living cells such as probiotic bacteria from environmental challenges. Up-to-date, various compounds with abilities to protect bacteria during freeze-drying and to increase viability during storage have been identified. In this study, alginate with calcium chloride was used to encapsulate probiotic bacteria using extrusion method. Then, effects of sucrose and skim milk as cryoprotectants and yeast powder containing beta-glucan as prebiotic on the survival of these bacteria were investigated.

The Homogeneous solution of bacteria with alginate and cry protectants were manually extruded into a calcium chloride solution. After 30 min of agitation, shaped beads were separated. For the comparison, bacterial population were enumerated in the primary culture, after encapsulation, freeze-drying and 1 week of storage at room conditions (N0, N, NF and N1w, respectively). To assess colony-forming unit per ml of the samples, first 1 g of fresh beads was dissolved in 9 ml of trisodium citrate and then serial dilution and pour plate techniques were carried out. Plates were incubated for 24-48 h and colonies were counted.

Results showed that encapsulation of bacteria with alginate and calcium chloride alone was 51% effective while use of yeast powder and sucrose with alginate increased the encapsulation efficiency to 97 and 99%, respectively. Furthermore, use of skim milk with alginate and sucrose resulted in the highest survival rate after 1 week of storage at room conditions. Therefore, encapsulation of probiotic bacteria with alginate layer and yeast powder containing prebiotics, sucrose and skim milk can be effective in survival of these bacteria.

Hyaluronic acid (HA) is a natural and linear polymer that finds a wide-range of applications in medicine, cosmetics, and nutraceuticals because of excellent viscoelasticity, high moisture retention capacity, high biocompatibility and non-toxicity. HA has been recently produced in industrial scale by Streptococcal species. Streptococci are nutritionally fastidious lactic acid bacteria and cannot synthesize some amino acids. Therefore, it is necessary to study and select some commercial culture media for their growth. In this study, HA production and hyaluronidase activity of S. zooepidemicus ATCC 43079 in three culture media were investigated. Regarding the detrimental effect of this enzyme on HA amount, 6-O-Palmitoyl-L-ascorbic acid as hyaluronidase inhibitor was added to culture medium during fermentation. The effect of three variables consisted of glucose concentration, yeast extract concentration and medium pH each at 3 levels were considered and (response surface methodology (RSM) was used for statistical design of experiments to study the HA production by this strain. The results showed that maximum HA production was obtained when glucose concentration, yeast extract concentration and pH were 21.2 g L-1, 43.6 g L-1 and 6.6, respectively. Under optimum conditions, HA was produced as 370±15 mg L-1 which was ~150% more than of HA concentration in basal medium (150±10 mg L-1) and productivity reached 56.74 g L-1 h-1 that was increased 2 fold compared to central point.

In order to targeted delivery of probiotics for food and drug applications and their effectiveness in preventing and treating various diseases, designing effective systems in this field can be helpful. In this paper, a new system for targeted delivery of probiotics has been introduced. The objectives of this study included: the efficiency of anti-acid microgels coated by multilayer polyelectrolyte formulation of alginate-chitosan for survivability of probiotic bacteria in gastric and intestinal simulation conditions. Tow Strains of probiotic bacteria including Lactobacillus Rhamnosus and Lactobacillus Plantarum were encapsulated separately in alginate hydrogels and calcium carbonate as an antacid agent (to control pH under acidic conditions) and coated with double bilayer alginate-chitosan by LbL self-assembly technique. The results showed that ( in the presence of pepsin enzyme and at pH=1.8 and in the presence of pancreatin enzyme and at pH=6.8), the survivability of these bacteria increased significantly compared to lactobacillus Plantarum and Lactobacillus rhamnosus 6 log(cfu/g) and 2.5 log(cfu/g) respectively. The number of viable cells in both probiotic strains was higher than the acceptable therapeutic level. In general, these results showed that these microcapsules can be used in controlled delivery of probiotics as food supplements successfully.

Codon optimization is an efficient approach to achieve a higher level of heterologous gene expression and generate productive recombinant mammalian cell lines. In our previous work, based on the codon usage preference of Chinese hamster ovary (CHO) cells, a codon-optimized human interferon-beta (opt-hIFN-β) gene was redesigned and transiently expressed in a suspension-adapted CHO (CHO-s) cell line. Our results indicated a 2.8-fold increase in the expression level of the codon-optimized gene compared to the unmodified sequence.

In the current work, based on our previous results, a stable CHO-K1 cell line expressing the opt-hIFN-β gene was engineered, in which the opt-hIFN-β gene expression was confirmed by dot and western blotting analyses.

The designed opt-hIFN-β sequence was digested and cloned into a pcDNA3.0 shuttle vector downstream to the cytomegalovirus (CMV) promoter. The verified recombinant plasmid was then linearized and transfected into a CHO-K1 cell line to integrate the opt-hIFN-β gene into the CHO-K1 genome. The transfected cells were then grown under the selective pressure of 450 µg/mL of G418 to develop a stable CHO-K1 cell line expressing the opt-hIFN-β gene. The enzyme-linked immunosorbent assay (ELISA) and dot and western blotting analyses were carried out to verify hIFN-β protein expression.

ELISA and dot and western blotting analyses confirmed the expression of hIFN-β in the stably-transfected CHO-K1 cells.

Stable expression of the opt-hIFN-β gene in the CHO-K1 cell line was verified by ELISA and dot and western blotting analyses. This study was a pioneering work for further production of recombinant hIFN-β in the bioreactor.

Age-related macular degeneration (AMD) is one of the retina diseases in which retinal pigment epithelium cells are degraded and lead to blindness. Available treatments only slow down the progression of it. In this study, human embryonic stem cells (hESCs) differentiated into retinal pigment epithelium cells were cultured on a polycaprolactone scaffold.

The optimization of the diameter of the produced scaffolds by electrospinning method was done using the fuzzy method for the first time. To improve cell adhesion and proliferation, related parameters to alkaline hydrolysis method were optimized and hydrophobic surface of scaffold was modified. After in vitro analysis, cells were cultured on different groups of scaffolds. In vivo analyses were done and cells culture on scaffolds observed.

The optimal parameters for the scaffold based on the fuzzy model were 18.1 kV for voltage, 0.07 g / ml for solution concentration and 115 nm for scaffold diameter, respectively. The immersion time of the scaffold in alkaline solution and concentration of solution were measured 97 min and 3.7 M, respectively. The treated scaffold had a higher degradation rate and water adsorption. MTT-Assay results showed that scaffolds with modified surfaces had a higher amount of cell viability and proliferation after 7 days. SEM image results confirmed this finding after almost two months. Additionally, the results of ICC test showed that after passing this time, cells kept their RPE and epithelium.

Based on the results, the hydrolyzed scaffold is a suitable substrate for cell proliferation and can be a good option for AMD treatment.

Codon optimization has been considered as a powerful strategy to increase the expression level of protein therapeutics in mammalian cells. As an empirical approach to study the effects of the codon usage and GC content on heterologous gene expression in suspension adapted Chinese hamster ovary (CHO-s) cells, we redesigned the recombinant human interferon beta (rhIFN-β) gene based on the codon preference of the CHO cell in a way to increase the GC content in the third position of each codon.

The nucleotide sequence of the codon-optimized rhIFN-β was synthesized in parallel with the wild-type and expressed transiently in CHO-s cells using Epstein-Bar virus (EBV)-based expression system. The protein expression of the rhIFN-β by codon-optimized and wild-type genes were quantified using ELISA test.

The results indicated a 2.8-fold increase in the expression level of the biologically active form of the rhIFN-β by codon-optimized sequence.

These results shed light on the capability of codon optimization to create a stable CHO cell for scaling up the production of recombinant therapeutics such as rhIFN-β. 

Lignocellulose is composed of cellulose, hemicellulose and lignin. Cellulose and hemicellulose are macromolecules of various sugars, while lignin is an aromatic polymer that made of phenylpropanoid precursors. Although cellulose, the main component of lignocellulose, is sensitive to biological degradation, but this polysaccharide is usually physicochemically bound to lignin in nature. Lignin is resistance to biodegradation and can protect cellulose against microbial attack. Lignocellulose degradation is important because has many applications in different industrial process and is used as raw material for production of the variety of biological products in different industries. Those strains employed in lignocellulose biodegradation, must have a strong and efficient enzymes in order to degrade these compounds. Some fungal strains belonging to white rot fungi are known as efficient microorganisms for degradation of lignocellulosic compounds. However, extensive researches have been carried out to improve bacterial and fungal strains for degradation of lignocellulosic compounds. In addition to the old and traditional methods such as mutagenesis, new strain improvement methods based on genetic modification have been proposed in order to increase the productivity of industrial processes. In this article, these kinds of methods have been explained in brief and some examples have been presented to show their applications for improvement of those strains are capable of degrading lignocellulosic compounds.

Hyaluronic acid (HA) is a major component of the extracellular epithelial, neural and connective tissue of vertebrates, as well as of extracellular microorganisms. This polysaccharide has specific applications in ophthalmology, orthopedic, cosmetics and tissue engineering due to features such as high viscosity and biocompatibility. Animal tissues and streptococci have a major role in producing hyaluronic acid, but because of problems such as protein contamination and the presence of endotoxin, attention has been drawn to the GRAS bacteria for producing hyaluronic acid. Lactobacilli are probiotic bacteria that have diverse uses. The production of biochemical macromolecules by this group of bacteria is a priority because they are GRAS. Hyaluronic acid production for the first time in these GRAS bacteria including Lactobacillus acidophilus PTCC1643, Lactobacillus rhamnosus PTCC1637, Lactobacillus casei PTCC1608 and Streptococcus thermophilus PTCC1738 were investigated. In the first step, Hyaluronic acid was isolated from specific culture medium and partially purified by ethanol precipitation daily for 96 hours. Carbazole method was used to measure the production of hyaluronic acid. Based on results, Lactobacillus rhamnosus produced about 0.4 g/l of hyaluronic acid at 96 hours. The increase of HA was also investigated using optimization culture medium by Taguchi design. By using this method, the optimum points of the factors were determined and the hyaluronic acid production increased by 162%.

The white rot fungi can produce different isoenzymes of extracellular oxidases such as lignin peroxidase, manganese peroxidase and laccase having ability to decompose lignin. Because of the non-specific nature of peroxidases produced by lignin-degrading system of white rot fungi, they can be used for degradation of a wide range of toxic and carcinogenic materials including industrial dyes. Laboratory studies on the ability and physiology of lignolytic system of white rot fungi demonstrated that it is promising to use these fungi for wastewater treatment of those companies which produce and consume industrial dyes. For large-scale treatment of wastewater containing dyes, it is necessary to immobilize these fungi on suitable carries in bioreactors. In this article, considering the metabolic and physiological characteristics of white rot fungi and their lignolytic system, the previous studies carried out on the degradation of dye wastewater using these fungi in free or immobilized form have been mentioned and their perspective has been also presented.

Amongst the methods that remove heavy metals from environment, biosorption approaches have received increased attention because of their environmentally friendly and cost-effective feature, as well as their superior performances.
In the present study, we investigated the ability of a surface-engineered Escherichia coli, carrying the cyanobacterial metallothionein on the cell surface, in the removal of Ca (II) from solution under different experimental conditions. The biosorption process was optimized using central composite design. In parallel, the kinetics of metal biosorption was studied, and the rate constants of different kinetic models were calculated.
Cadmium biosorption is followed by the second-order kinetics. Freundlich and Langmuir equations were used to analyze sorption data; characteristic parameters were determined for each adsorption isotherm. The biosorption process was optimized using the central composite design. The optimal cadmium sorption capacity (284.69 nmol/mg biomass) was obtained at 40°C (pH 8) and a biomass dosage of 10 mg. The influence of two elutants, EDTA and CaCl2, was also assessed on metal recovery. Approximately, 68.58% and 56.54% of the adsorbed cadmium were removed by EDTA and CaCl2 during desorption, respectively. The Fourier transform infrared spectrophotometer (FTIR) analysis indicated that carboxyl, amino, phosphoryl, thiol, and hydroxyl are the main chemical groups involved in the cadmium bioadsorption process.
Results from this study implied that chemical adsorption on the heterogeneous surface of E. coli E and optimization of adsorption parameters provides a highly efficient bioadsorbent.

Probiotics have to reach their site of action in certain numbers in order to exhibit positive health effects. Encapsulation has shown remarkable enhancing effects on probiotic survival in simulated gastric conditions compared to free bacteria. The purpose of this study was identification and evaluation of a potential probiotic strain using encapsulation process by new carriers in order to improve probiotic viability during in vitro simulated conditions.
Material and A native Lactobacillus was isolated from yogurt, identified as Lactobacillus casei PM01 (NCBI registered) and analyzed for probiotic properties alongside established probiotic strains of Lactobacillus acidophilus ATCC 43556, and Lactobacillus rhamnosus ATCC 7469. Acid and bile resistance, adhesion to Caco-2 cells and antibiotic resistance were evaluated. Lactobacillus casei PM01 was encapsulated with alginate, chitosan and natural branched polysaccharides (pectin, tragacanth gum and gum Arabic) by using extrusion technique. Encapsulation efficiency, acidification activity and viability of entrapped Lactobacillus casei PM01 in simulated gastric pH were determined.
Results and Based on the results, all the three strains could be considered as potential probiotics, and are good candidates for further in vitro and in vivo evaluation. The results showed that the survival of encapsulated Lactobacillus casei PM01 was significantly (p≤0.05) increased when it was incubated in simulated gastric pH. It can be concluded that indigenous Lactobacillus casei PM01 in encapsulated form is introduced as an efficient probiotic strain for using in dairy products.
Conflict of interest: The authors declare no conflict of interest.

Identification and use of more efficient enzymes in the food and pharmaceutical industries is the focus of many researchers. The aim of this study was to search for a new bacterial strain capable of producing high levels of pullulanase applicable to biotechnology, the starch bioprocessing and food industries. A new pullulan hydrolyzing Bacillus strain was isolated and designated SDK2. Morphological and biochemical tests identified the strain as a putative Bacillus cereus strain, which was further characterized and confirmed through 16s rRNA sequencing, and was submitted to GeneBank, under the accession number FR6864500. Quantative analysis of the strain’s pullulanase activity was carried out by the Dintrosalicyclic (DNS) acid-based assay. Thin layer chromatography (TLC) of the culture supernatant, identified the extracellular pullulanase as neopullulanase. Effects of temperature and pH on pullulanase activity were also studied. The optimum conditions for enzyme activity, as represented by 60o C and a pH of 7, resulted in an activity of 13.43 U/ml, which is much higher than some of the previously reported activities. However, growth of B. cereus SDK2 was also observed at a pH range of 5 to 10, and temperatures of 30 oC to 50 oC. The effect of metal ions and reagents, such as Mg+2, Ca+2, Zn+2, Cu+2, Fe+2, Ni+2 on enzyme activity showed that Ca+2 ions increased pullulan activity, whereas the other ions and reagents inhibited pullulanase activity. The ability of B. cereus SDK2 to produce high levels of neopullulanase stable at 60 oC that can generate panose from pullulan, make this newly isolated strain a valuable source of debranching enzyme for biotechnology, the starch bioprocess and medical industries.

Chitosan nanoparticles have become of great interest for nanomedicine, biomedical engineering and development of new therapeutic drug release systems with improved bioavailability, increased specificity and sensitivity, and reduced pharmacological toxicity. The aim of the present study is to synthesis and optimization of chitosan nanoparticles for industrial and biomedical applications. Fe3O4 was synthesized and optimized as magnetic core nanoparticles and then chitosan covered this magnetic core. The size and morphology of the nano-magnetic chitosan was analyzed by scanning electron microscopy (SEM). Topography and size distribution of the nanoparticles were shown with two-dimensional and three-dimensional images of Atomic Force Microscopy (AFM). The nanoparticles were analyzed using Transmission Electron Microscopy (TEM). The chitosan nanoparticles prepared in the experiment exhibited white powder shape. The SEM micrographs of the nano-magnetic chitosan showed that they were approximately uniform spheres. The unmodified chitosan nanoparticles composed of clusters of nanoparticles with sizes ranging from 10 nm to 80 nm. AFM provides a three-dimensional surface profile. The TEM image showed physical aggregation of the chitosan nanoparticles. The results show that a novel chitosan nanoparticle was successfully synthesized and characterized. It seems that this nanoparticle like the other chitosan nano particles has potential applications for nanomedicine, biomedical engineering, industrial and pharmaceutical fields.

Lipases are valuable biocatalysts which are widely used in the detergent, food, dairy and pharmaceutical industries. The aims of the present study included the isolation of a lipase-producer from industrial zones and the partial characterization of the enzyme. A number of bacteria were isolated from sites related to the oil industries. An isolate forming a halo zone in a selective medium (TW agar) was then selected and grown on a medium suitable for the production of lipase. The isolate was subsequently identified by the 16S rRNA sequencing method, and its enzyme activity was measured by a spectrophotometer using pNPP as a substrate. The selected isolate was identified by the molecular method as Pseudomonas sp. Its extracellular lipase activity was 41.5 ± 1.4 U/ml, and the high affinity of this enzyme for the substrate was indicated by the kinetic parameters of Km and Vm, which were estimated by the the Lineweaver-Burk plot as 0.77 mM and 49.5 U/ml, respectively. Activation energy of lipase calculated from the Arrhenius plot was found to be 20.78 kJ/mol, and a temperature coefficient (Q10) of 4.39 indicated the high catalytic activity of the enzyme and the temperature dependence of the enzymatic reaction. The results demonstrated that the indigenous isolate could have potential applications in many relevant industries.

Aims and Amylases are one of the major industrial enzymes that occupy 25 % of the world enzyme market. These enzymes are used in many different areas، such as paper، textiles، pharmaceutical، food، starch saccharafication and processing industries. Much research has been carried out regarding application of amylolytic enzymes produced by the genus Bacillus، to the production of glucose and beverages، food and detergent industries. Because of the extensive applicability of amylolytic enzymes، research in relation to identification of these enzymes and their characteristic is continuously being carried out. Hence، the aim of this research was to investigate the amylolytic enzyme profile of a native Bacillus strain، and determine its enzyme characteristics. In this study، the enzymatic profile of the bacterium، Bacillus amyloliquefaciens BEH 111، was determined by using the SDS-PAGE، zymogram and TLC methods. Zymography and TLC were used to identify the amylolytic enzyme profile of the bacterium. The molecular weight of α-amylase was estimated by SDS-PAGE. The 3، 5-Dinitrosalisyclic acid (DNS) indicator was used to examine α-amylase activity، quantitatively. Investigation of enzyme characteristics and determination of maximal enzyme activity was carried by the DNS method، at different temperatures، pH values، substrate concentrations and time periods. The molecular weight of α-amylase was estimated to be 55 kDa by SDS-PAGE. Investigation of enzyme characteristics showed that maximum α-amylase activity was achieved at a temperature of 50oC، pH 7، presence of 2% starch، during a 90 min time period. Enzyme activity obtained under these conditions was 8222 U/L. The high level of enzyme activity produced by B. amyloliquefaciens BEH 111 can thus be of commercial significance. Furthermore، by having activity at 50oC and above، makes it possible for this enzyme to be applied to processes that use high temperatures. The optimized pH levels of 6-7 that resulted in high enzyme activity can also allow the potential use of this enzyme in processes such as starch liquefaction and gelatinization.

The high cell density cultivation (HCDC) of a recombinant E. coli producing human growth hormone (hGH) under different heat induction strategies has been reported. In this paper the effect of heat shock temperature, its duration and post-induction temperature, at two levels on cell growth and death, hGH production and its degradation, substrate utilization and by-product formation were investigated by full factorial experimental design. The results showed that heat shock temperature was the most effective factor on hGH production having approximately 75.8% of total contribution. There was no significant accumulation of substrate or by-product in culture medium during HCDC in all experiments. Thirty two percent of cells were subjected to lysis during the heat induction at 42C for 20 min followed by 37C for 4h. Biologically active recombinant hGH was produced comprising 13% of total cell protein without degradation. An empirical equation was employed to describe the relationship between three factors and hGH production during HCDC.

Poly-β-hydroxybutyrate (PHB) is a biodegradable polymer which is regarded as a new environmentally compatible material. A wide variety of micro-organisms accumulate poly-β-hydroxybutyrate within cells as an intracellular storage material of carbon and energy. In this study, PHB was synthesized by Ralstonia eutropha (formerly Alcaligenes eutrophus) in a defined medium consisted of fructose as a sole carbon source. The effect of four process variables was studied to optimize the biosynthesis of PHB in bench scale. The results showed that the fresh inoculum at the mid-exponential phase lead to more growth during fermentation. The optimum shaking rate and temperature were 250 rpm and 25°C, respectively. The high concentration of fructose inhibited the growth, so it was optimized at 15 gL-1. Under these conditions, PHB was accumulated as inclusion bodies so that 70% of the dry cell weight of Ralstonia eutropha was composed of PHB. The yield coefficients of biomass and product were 0.3 and 0.21 g.g-1, respectively.