A structured unsegregated cybernetic model is able to describe diauxic growth phenomena of cells colony in aerobic condition. This model shows that the metabolic activity of the cells is regulated by internal cellular controls which direct the micro-organism towards the most convenient metabolic pathway able to optimize the use of available resources. In this paper, for proving this reality, a structured unsegregated cybernetic model have been used for describing of the growth stages of Saccharomyces cerevisiae on mixed substrates. The results of simulation of baker’s yeast in batch and fed-batch bioreactor show that agreements are quite satisfactory between experimental data and simulation results. And it well performs in the simulation of the lag-phases and the diauxic growth. Finally, for preventing of oxygen starvation that causes ethanol production, oxygen mass transfer coefficient is simulated on the function of impeller speed and air flow rate and the effect of this parameter on biomass yield have been discussed.

The polite listener In England stares at the speaker attentively and blinks his eyes occasionally as a sign of interest. That eye-blink says nothing to Americans, who expect the listener to nod or to murmur something such as "mm - hmm”. And in some parts of  Far East, it is impolite to look at the other person at all during conversation.It is often argued that, in teaching foreign languages, culture and language are interwoven in a way that it is not possible to present language without its culture. However, until a new method of teaching language, called communicative approach, which is sociolinguistically oriented, had not come into existence, this belief was not used to be observed in textbooks and language classes. This method intends to create situations in the classroom in which foreign language can be used as naturally and authentically as the native speakers of target language use it for communicative purposes.The problem of teaching culture, nevertheless, does not end here. Nowadays, foreign languages are taught with different and varied objectives. Is it necessary for all foreign language learners to get familiar with the culture of foreign language they are supposed to learn? As Schumann (1984) claims, is it true that second language learning is impossible, unless one gives up his/her own native culture and adopts the culture of foreign language community? What are some relevant issues regarding teaching English in Iran? These are actually some basic questions raised in this article. Whereas definite answers are not necessarily provided in this paper, some areas of research related to culture, and teaching foreign language are put forward.

Biodesulfurization of coal has been carried out in batch culture of single strain and mixed culture of sulfur oxidizing bacteria. The pure cultures of Thiobacillus thiooxidans and Thiobacillus ferrooxidans utilized inorganic sulfur content of Malaysian coal. The chemolithotroph bacteria were able to grow on coal and metabolize the coal's sulfur content. The batch cultures of coal with 3-5 percent sulfur were used for growing microorganisms. A few species of bacteria and fungi had potential to utilize coal complex media, which were isolated from coal rice hulls and pharmaceutical wastewater. Asperigillus niger and Thiobacillus species isolated from coal, fungi from rice hulls and Saccharomyces species from wastewater, all microorganisms capable to grow on coal. The main concern was the sulfur oxidizing bacteria were screened out from all non-sulfur reducing bacteria. In the Batch cultures, the biooxidation coal's sulfur was affected by several parameters, such as pH, nutrients, agitation rate, growth stimulants and percentage coal. The trace amount of magnesium and cobalt ions, 200 rpm agitation rate with initial pH of2.6 for mixed culture of Thiobacillus thiooxidans and Thiobacillus ferrooxidans showed maximum growth rate and optimum batch operating conditions. The highest sulfur oxidation was obtained at the optimal Thiobacillus growth rate. Morethan 75 percent of sulfur was removed from coal. The biooxidation of coal, the kinetic model followed by Monod rate equation with specific growth rate,  mmax= 4.8 d-1 and rate constant, Ks = 16.7 g/L.

Lactic acid is an organic acid which have a wide range of application in different industries. Novel applications in synthesis of biodegradable plastics have increased the demand for lactic acid.The aim of present research was to investigate the effect of Temperature, PH and different nitrogen source, on the production of lactic acid from deproteinized cheese whey using Lactobacillus bulgaricus (ATCC 8001, PTCC 1332) as the producer organism in a batch culture. The initial lactose concentration was 40 g/Lit. Various nitrogen sources were compared with yeast extract in terms of their efficiency for lactic acid production. Process was performed at 72 hour incubation time with no pH control. Highest lactic acid production and efficiency was 24.8 g/Lit. and 0.62% respectively, for medium containing 40 g/Lit. lactose and 20 g/Lit. yeast extract. And also optimal temperature for cell growth and lactic acid production was 32oC and appropriate pH investigated at 6-6.5.

In the present study, the microbial production of hyaluronic acid by wild type Streptococcus zooepidemicus in semi defined medium in shake flask and 5 liters fermenter has studied. At first the culture condition and medium composition optimized. To experimental design, L-9 array of taguchi approach is used. The effects of glucose, yeast extract, sulphate and phosphate salts concentration and medium pH on hyaluronic acid production in batch culture in shakeflask was studied. Based on experimental data analysis, optimum condition for hyaluronic acid production was: 30 g/L glucose, 20 g/L yeast extract, 7.5 g/L sulphate and phosphate salts and medium pH 7. Of the culture condition examined, the yeast extract concentration had the most pronounced effect on the hyaluronic acid production. In optimum condition, hyaluronic acid production at 206 mg/L and 800 mg/L, in shake flask and 5 liters fermenter, in batch culture was obtained.

In this paper, dextranase produced by a high dextranase-producing mutant strain of Penicillium lilacinum was purified and was considered for kinetic investigation. It has been shown that the optimum pH and temperature for enzyme activity were 4.5 and 55°c, respectively. The enzyme was stable at pH of 5.5-6 and temperatures up to 60°c during 45 min incubation. Under optimal conditions, the kinetic parameters of Km and Vrnax were obtained as 5.78 mg/ml and 0.379 mmole maltose monohydrate/min, respectively. The effects of the most likely inhibitors present in the juice were also studied and it was found that glucose, sucrose, raffinose, galactose and dextran competitively inhibit the enzyme activity, while mixed-type inhibition was observed by maltose, pectin and galactronic acid. Finally, the enzyme activity was improved by addition of glycerol, sorbitol and egg albumen. The results were in good agreement with the experimental data obtained for the existing conditions in Bisotoon Sugar Factory.

Modeling and simulation of Polyhydroxybutyrate (PHB) production by Protomonas extorquens in fed-batch culture were conducted in this research. The fed-batch model, developed for this process, employed a kinetic model proposed by other researchers. Several kinetic models were investigated to choose the best model. The criterion for this selection was goodness of fit d2. Haldane kinetic model was selected since it leads to the lowest d2. Experimental data that have been used in this study were extracted from literature. The kinetic model was then incorporated into the process model. The values of process model parameters were estimated by employing an optimization routine developed in this study and using two sets of experimental data. These data were obtained applying two different methods of fed-batch cultivation. The values of d2 for these two methods were 2.5 and 0.0016 respectively. Finally, simulation results were compared with two other sets of experimental data to validate the model.