Iranian Journal of Biotechnology
Year:2011 | Volume:9 | Issue:2|Papers Count:10

Arachidonic acid is an essential fatty acid in human nutrition. In the present study, production of arachidonic acid by Mortierella alpina CBS 754.68 was evaluated in submerged fermentation. The fermentation variables were selected in accordance with the Plackett- Burman (PB) design and further optimized via response surface methodology (RSM). Five significant variables, namely glucose, yeast extract, temperature, agitation rate, and fermentation time were selected for the optimization studies. The statistical model was constructed via central composite design (CCD).Following the optimization step arachidonic acid production increased by approximately 660.5%, when compared to the screening step. The results indicate that carrying out the fermentation under the conditions of glucose at 50 g/l; yeast extract at 14 g/l; temperature of 22oC; agitation rate of 180 rpm, and fermentation time of 8 days will increase the arachidonic acid production up to 3 g/l. Results show that the optimization of culture conditions could greatly increase arachidonic acid production by Mortierella alpina CBS 754.68.

The purpose of this study was to utilize low quality date syrup, a rich and available source of nutrient in Iran, for the production of bacterial cellulose using Gluconacetobacter xylinus. Static batch fermentation for the purpose of cellulose production by G. xylinus (PTCC, 1734) was studied using low quality date syrup and sucrose solution (Bx.10%) as fermentation media at 28°C. Results showed that maximum yields of bacterial cellulose after 336 h fermentation were 4.35 and 1.69 g/100 ml of date syrup and sucrose media, respectively. The FT-IR spectrum of commercial plant cellulose as a standard was similar to that of bacterial cellulose. To determine the physical structure of the bacterial cellulose and standard cellulose fibers, scanning electron microscopy (SEM) was carried out. The results revealed more delicacy in structure of bacterial cellulose. Determination of crystallinity of the samples using X-ray diffractometry demonstrated that the crystallinity level of standard cellulose (83.61%) was more than that of bacterial cellulose (60.73%). This study obviously showed the ability of low quality date syrup, a suitable and cheap carbon source, to be used as a substrate in a fermentation medium for production of cellulose by Gluconacetobacter xylinus.

L-asparaginase is an anti-neoplastic agent used in the chemotherapy of lymphoblastic leukaemia. The present work deals with production of extra-cellular Lasparaginase from marine actinomycetes, using submerged fermentation. Marine actinomycete Streptomyces associated with marine sponge Callyspongia diffusa was isolated using specific ISP medium. Sponge-associated Streptomyces was characterized by conventional methods, and identified as Streptomyces noursei MTCC 10469. Production of Lasparaginase by submerged fermentation was carried out using medium Tryptone Glucose Yeast extract (TGY) broth. The enzyme was purified to near homogeneity by ammonium sulphate precipitation, dialysis, gel filtration on Sephadex G-100 column, CM Sephadex C-50 and SDS-PAGE. The enzyme was purified at 98.23 folds, and showed a final specific activity of 78.88 IU/mg, with 2.14% yield. SDS-PAGE of the purified enzyme revealed an apparent molecular weight of 102 kDa for it. The optimum pH, temperature and incubation time of L-asparaginase was found to be 8, 50ºC and 35 min, respectively. The study suggests that marine actinomycetes, particularly Streptomyces, may be used as a potential source of L-asparaginase.

The yeast strains that are resistant to high concentration of ethanol have biotechnological benefits and are suitable models for physiology and molecular genetics research fields. A novel ethanol-tolerant mutant strain, mut1, derived from the commercial Saccharomyces cerevisiae showed higher ethanol production, and also demonstrated resistance to ethanol but not to other alcohols, such as methanol, 2-propanol, and 1- butanol. To characterize mut1, the strain’s resistance to other organic compounds and osmotic and cell wall stresses were examined. The growth of the mut1 strain in the presence of ethyl n-caproate and 3-methyl butyl acetate, which were metabolic derivatives of ethanol, was found to be less than the wild type. On the other hand, the growth of the mut1 strain in the presence of 50% (w/v) sucrose and 1M NaCl was similar to that of the wild type. The sensitivity to cell wall digestive enzyme, zymolyase, was also similar in both wild and mut1 strains. Finally, the mut1 strain showed resistance to homocysteine and serine but was sensitive to methionine. These results suggest that the ethanol resistance of the mut1 strain may be more related to the ethanol metabolic and signalling pathways rather than the enhanced stress resistances relating to the membrane or cell wall compositions.

Bovine spongiform encephalopathy (BSE) is a fatal infectious neurodegenerative disease in cattle, characterized by the accumulation of an abnormal, proteaseresistant prion protein (PrPSc) in the brain. BSE is similar to scrapie in sheep and goats and Creuzfeldt- Jakob disease in humans. Susceptibility in cattle has been shown to be under the influence of two polymorphic locations, which are a 23 bp in/del polymorphism and a 12 bp indel within intron 1 of the prion protein gene (PRNP). DNA was extracted from blood samples of three Iranian cattle populations including Sistani (Bos indicus) (n=60), Golpayegani (Bos indicus) (n=62) and Iranian Holstein (Bos taurus) (n=50), In order to identify the putative polymorphisms of the PRNP gene of those breeds. Allele, genotype and haplotype frequencies of the polymorphisms were determined for the three populations. Susceptibility analysis was considered as per literature, upon which, it was suggested that the two Bos indicus native populations are more resistant to BSE than the Iranian Holstein (Bos taurus), due to higher gene frequency for insertion allele of the intron 1 of the PRNP gene polymorphism.

In order to investigate the molecular diversity of mtDNA in Azeri population, 133 Azeri subjects inhabiting different regions of Azerbaijan (Iran) were selected.Blood samples were taken from these subjects for mtDNA extraction. The extracted mtDNA samples were then studied by the PCR-RFLP method.Fourteen haplogroups were characterized from which 82% were identified as European specific haplogroups.The H haplogroup was the most frequent and 79 haplotypes were specified. In this study, the Iranian Azeri population was found to be a heterogenic population where all the specific haplogroups of Asians, Europeans and Africans were present in the studied population. Comparing the haplogroups of the present investigation with other populations indicated a very close similarity with other Iranian populations, but was different from haplogroups of other Asian populations who also speak the Azeri language.

Heme oxygenase-2 (HO-2) is a critical antioxidative stress enzyme found in endothelial cells and adventitial nerves. This enzyme in conjunction with other HOs (1 and 3) metabolize heme molecule into ferrous iron, carbon monoxide (CO), and biliverdin which is further converted to bilirubin. Both biliverdin and bilirubin are potent antioxidants, reducing the risk of atherosclerosis.HO-2 also induces endothelial relaxation by synthesizing CO. This is the first study to evaluate the association of HO-2 gene mutation in patients affected with atherosclerosis. Blood samples from patients (n=137) and normal controls (n=100) were collected.Three pairs of primers were designed to amplify exons 2 to 4 related to human HO-2 gene. The PCR products were analyzed by SSCP and sequencing to find out mutations. Iron and bilirubins (Total, Direct and Indirect) levels were determined in patients and controls.Two nucleotide substitutions were found among 10% of patients, consisted of a newly reported transversion mutation, C to A substitution in codon A70D (GCC to GAC) (Ala to Asp) and a previously reported transition mutation, A to G substitution in codon K89E (AAG to GAG) (Leu to Glu). Significant associations were obtained between risk of atherosclerosis and A437G substitution in codon K89E of HO-2 gene (P< 0.006 and c2>6.82) and reduced level of total (P< 0.016 and c2>6.01), and indirect (P<0.016 and c2 >5.99) bilirubins with no significant association with serum iron and direct bilirubin. No significant associations were observed among C381A substitution in codon (A70D, P<0.11 and c2>2.97), level of serum iron, bilirubin and risk of atherosclerosis. These findings indicate the importance of A437G substitution in the development of atherosclerosis. Further studies are required to study the association of HO-2 gene mutations with atherosclerosis in other populations.

In this study the ability of Acidithiobacillus ferrooxidans, with regard to the biorecovery of heavy metals in shake flask has been investigated. Adaptation experiments with the single metal ions Ni, Co, V, Mo, W and a mixture of the first four metal ions in the medium was developed through serial sub-culturing. Adaptation showed that A. ferrooxidans could tolerate up to 2.3 g/l Ni, 1.4 g/l Co, 1.4 g/l V, 0.045 g/l Mo and 0.005 g/l W, singly. In the presence of multi-metals considering a mixture of Ni-Co-V-Mo, the bacteria was able to tolerate up to 1.5 g/l Ni, 0.8 g/l Co, 0.8 g/l V and 0.05 g/l Mo in steps of 50-100 mg/l for Ni, Co and V, while for Mo and W with increments in concentration of 1-5 ppm, because of the high toxicity of these two metals to the bacteria. Adaptation of the bacterial strain was carried out in batch cultures by continually growing the bacteria in an environment containing increasing concentrations of the toxic metal such that a culture tolerant to the toxic metal proliferates. Effects of several variables such as pH, Eh, bacterial concentration in the solution as well as its resistance to heavy metals and ferrous and ferric iron concentration for the specific bacterial growth rate, were also investigated. This study showed that the various concentrations of Ni, Co and V had little effect on the oxidation of ferrous iron or the cell growth of A. ferrooxidans, whereas Mo and W ions were very inhibitory towards the Fe+2 oxidation ability of A. ferrooxidans.

Calpastatin is an endogenous inhibitor of calpain (calcium- dependent cysteine protease). Calpastatin activity is highly related to the rate of protein turnover and rate of meat tenderization. In order to characterize the structure of calpastatin in Iranian Afshari breed of sheep, intron 6 and partial exon 7 of the L domain were amplified and sequenced. A fragment of approximately 1.5 kb was identified. In this study, an Afshari calpastatin gene fragment that encoded L Domain amino acids was detected. Hence by detection of such conserved mutations, it is possible to use these polymorphisms in Marker-Assisted Selection (MAS).