Reduction of chemical and biological oxygen demands from oil wastes via oleaginous fungi: an attempt to convert food by products to essential fatty acids

Background: the production of waste pollutants has become a major problem for many food and oil industries. However, oil wastes can provide alternative substrates for industry, which could help to solve environmental pollution problems. Furthermore, oil wastes can be used as substrates to produce unsaturated fatty acids, which are important for health

Objectives: the production of fatty acids in fungi using oil wastes and renewable substrates were investigated

Material and Methods: oil waste sources were obtained from food factories and restaurants [F1, F2, F3, R1, and R2]. Cunninghamella echinulata DSM1905 and Rhizopus stolonifer DSM2194 were used to treat the wastes. Changes in lipid and fatty acid contents, biomass, and pH were monitored

Results: C. echinulata produced about 18.4 and 20.1% gamma linolenic acid [GLA] from the R1 and R2 oil wastes, respectively. It also produced 9.3% and 12.4% linolenate from the F2 and F3 wastes. R. stolonifer produced 21% GLA from R1 and 9.3% linolenate from F3. C. echinulata reduced biological oxygen demand [BOD] and chemical oxygen demand [COD] by 67%-74% and 50%-98%, respectively. R. stolonifer reduced BOD by 36%-74% and COD by 10%-78%

Conclusions: this study emphasized the abilities of oleaginous fungi to utilize oil wastes as carbon sources to reduce BOD and COD of the wastes, producing essential fatty acids

Application of Taguchi design and Response Surface Methodology for improving conversion of isoeugenol into vanillin by resting cells of Psychrobacter sp. CSW4

For all industrial processes, modelling, optimisation and control are the keys to enhance productivity and ensure product quality. In the current study, the optimization of process parameters for improving the conversion of isoeugenol to vanillin by Psychrobacter sp. CSW4 was investigated by means of Taguchi approach and Box-Behnken statistical design under resting cell conditions. Taguchi design was employed for screening the significant variables in the bioconversion medium. Sequentially, Box-Behnken design experiments under Response Surface Methodology [RSM] was used for further optimization. Four factors [isoeugenol, NaCl, biomass and tween 80 initial concentrations], which have significant effects on vanillin yield, were selected from ten variables by Taguchi experimental design. With the regression coefficient analysis in the Box-Behnken design, a relationship between vanillin production and four significant variables was obtained, and the optimum levels of the four variables were as follows: initial isoeugenol concentration 6.5 g/L, initial tween 80 concentration 0.89 g/L, initial NaCl concentration 113.2 g/L and initial biomass concentration 6.27 g/L. Under these optimized conditions, the maximum predicted concentration of vanillin was 2.25 g/L. These optimized values of the factors were validated in a triplicate shaking flask study and an average of 2.19 g/L for vanillin, which corresponded to a molar yield 36.3%, after a 24 h bioconversion was obtained. The present work is the first one reporting the application of Taguchi design and Response surface methodology for optimizing bioconversion of isoeugenol into vanillin under resting cell conditions

Characterization of an interesting novel mutant strain of commercial Saccharomyces cerevisiae

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

[ brief review of yeast two-hybrid system]

Protein interactions are essential to all cellular processes, such as replication, transcription, splicing, translation and metabolism. The yeast two-hybrid system utilizes the reconstitution of an active transcription factor for assay for protein-protein interactions. The active transcription factors are formed as a dimmer between two fusion proteins, one of which contains a DNA-binding domain [DB] fused to the first protein of interest [DB-X Bait] and the other, an activation domain [AD] fused to the second protein of interest [AD-Y; Prey or Target protein]. DB-X: AD-Y interaction reconstitutes a functional factor that activates chromosomally integrated reporter genes driven by promoters containing the relevant DB binding sites. When a selectable marker gene such as HIS3 is used as a reporter gene, two-hybrid dependent transcription activation can be monitored by growth of yeast cells on plates lacking histidine, thereby providing a tool for detection of protein-protein interactions. Nowadays, yeast two-hybrid system is considered as a suitable approach for mapping of protein interactions in cells. This map may consist of many possible protein interactions that occur during the entire lifespan of a cell. In this review, we are going to describe this system, its efficiencies and its approaches for protein-protein interactions

[Application of genetic engineering in changing of saccharomyces cervisiae metabolism]

Saccharomyces cerevisiae is the most important industrial yeast for production of biochemical components, recombinant proteins and single-cell protein. We can use various genetic engineering methods for changing of yeast metabolic pathway[s] to increase of substrate source range such as xylose and lactose, increase of production efficiency and facilitate of industrial fermentation process. These modifications are discussed in new phylome of biology named "metabolic engineering". Here we are going to introduce a brief expression of this scientific field