دانلود مقاله ترجمه شده تولید ال – لیزین توسط گلوتامیکوم کورینه باکتریوم – مجله الزویر

فهرست مطالب:

 چکیده
۱ مقدمه
۲ روش ها
۲ ۱ میکروارگانیسم
۲ ۲ محیط کشت و شرایط تخمیر
۲ ۳ طرح های ازمایشی
۲ ۴ مطالعات تحلیلی
۳ نتایج و بحث
۳ ۱ بهینه سازی محیط کشت
۳ ۱ ۱ طرح ازمایشی ۱
۳ ۱ ۲ طرح ازمایشی ۲
۳ ۲ مقایسه ی بین محیط های بهینه و محیط های اولیه

بخشی از ترجمه:

 شکل ۱ تغییرات زمانی بیوماس و تولید و مصرف گلوکز را برای محیط های اولیه و بهینه نشان می دهد. ترکیب محیط بهینه با ۷ تکرار در دومین طرح ازمایشی به شکل ذیل بود سیلاژ ماهی ۴۰ گرم بر لیتر،گلوکز ۱۴۰ گرم بر لیتر، (NH4)2SO4 75 گرم بر لیتر، K2HPO4 1 گرم بر لیتر، KH2PO4 1 گرم بر لیتر، MgSO4 _ 7H2O, 0.4 گرم بر لیتر ، MnSO4 _ 4H2O 10 میلی گرم، FeSO4 _ 7H2O 10 میلی گرم، thiamine–HCl 300 میکرو گرم،بیوتین ۴۰۰ میکروگرم بودند محیط اولیه در بخش روش توصیف شد.
غلظت نهایی بیوماس و به ترتیب تا ۲٫۵ و ۲٫۶ درصد در ۷ تکرار در مقایسه با محیط اولیه افزایش پیدا کرد. تولید برای محیط بهینه در شانزدهمین ساعت بعد از محیط اولیه شروع شد. مقدار گلوکز مصرف شده بسیار بیشتر از محیط بهینه بود. این نتایج نشان دادند که محیط بهینه منجر به افزایش رشد میکروبی و در نتیجه تولید بهتر در مقایسه با محیط اولیه شده است. تولید حجمی   به طور معنی داری در محیط بهینه   در مقایسه با محیط اولیه   افزایش پیدا کرد با این حال تولید ویژه در ۷۲ ساعت در هر دو مورد مشابه بود(با لا تر از ۳ گرم لیزین بر گرم سلول).محیط بهبنه موجب تولید بیوماس بیشتر با افزایش محصوص در ضریب تبدیل سوبسترا شد(  در برابر ۰٫۳۲ گرم بر گرم در محیط اولیه). در عین حال تولید فراورده های جانبی نظیر اسید های لاکتیک و استیک به ترتیب ۷۰ و ۱۰ میلی مول در محیط اولیه بر خلاف محیط بهینه شده بود که مقدار اسید لاکتیک ۶۰ میلی مول و مقدار اسید استیکی مشاهده نشد.

بخشی از مقاله انگلیسی:

Introduction L-lysine is the third most abundantly produced amino acid at the industrial scale. Eighty per cent is produced by fermentation and 20% by chemical synthesis. In the fermentative processes, the culture medium is the major financial input and N-source is usually the most expensive component. Potential N-sources include various inorganic (ammonium or nitrate salt) or organic compounds (yeast extract, corn steep liquor, soybean protein hydrolysate), and various other extracts of vegetal and animal tissues (Bisaria et al., 1997). By-products of seafood have a high potential as cheap N-sources for microbial growth (Vecht-Lifshitz et al., 1990). Silage produced from fish wastes (whole heads, fins, skeletal debris, shrimp by-catch captures, and under-utilised whole species of fish) results in a stable product containing peptides and amino acids with high nutritional value (Raa and Gildberg, 1982). The use of fish silage instead of yeast extract has been reported for L-lysine microbial production (Coello et al., 2000). In the last decades, statistical experimental methods have been applied to media optimisation for industrial purpose. These designs include the blocking and factorial experiments for determining the path of steepest ascent, in order to identify the effect of individual factors and to approach the neighbourhood of the optimum response (Box et al., 1978). Furthermore, response surface methodology (RSM) is suitable for describing a near-optimum region and thus for exactly investigating optimum conditions for a multifactorial system. RSM and central composite designs has been successfully used to produce enzymes, biomass, and metabolites (Udeh and Achremowicz, 1993; Saval et al., 1993; Ergum and Mutlu, 2000). We used two successive fractional factorial designs (FFDs) followed by a RSM to optimise a medium containing fish silage, glucose, and eight inorganic salts for L-lysine production by Corynebacterium glutamicum. A comparison between the original and the optimised media for biomass and L-lysine productions, and glucose consumption, is presented. 2. Methods 2.1. Microorganism The L-lysine producing strain, designated as GIGO, isolated from soil in aerobic conditions, was used in this work. Biochemical tests conducted on the GIGO strain in our laboratory were confirmed by the Pasteur Institute of France, which characterised the isolate as C. glutamicum. It was maintained on 25% (v/v) glycerol at
۷۰ C by CVCM-IBE strain culture collection (Venezuela). 2.2. Culture media and fermentation conditions The inoculum (10% (v/v)) and fish silage medium was based on a previous study by Coello et al. (2000) and had the following composition per liter: fish silage, 40 g; glucose, 140 g; (NH4)2SO4, 75 g; K2HPO4, 1 g; KH2PO4, 1 g; MgSO4 7H2O, 0.4 g; MnSO4 4H2O, 10 mg; FeSO4 7H2O, 10 mg; thiamine–HCl, 300 lg; biotin, 400 lg. Fish silage was prepared as described by Bello et al. (1993). Fermentation runs were performed in 500 ml-baffled Erlenmeyer flasks (20 ml culture volume) at 30 C for 72 h on a rotary shaker at 250 rpm. Samples were withdrawn at intervals to measure dry cell mass, Llysine production, organic acids excretion and residual glucose. The original and optimised media were compared two-fold in triplicate using the same conditions. The purity and auxotrophy characteristics of the strain were determined each time by culture on appropriate agar plates. 2.3. Experimental designs The optimisation of the culture medium was performed in two steps. First, 10 compounds were considered within a 210–۶ FFD, in order to determine which compounds had a major influence on L-lysine production (Table 1). Each variable was evaluated at a high (þ۱), a low (
۱), and a central level (0), that was repeated four times to estimate the experimental variability. Data were fitted to a first-order model (Table 2). In a second step, five of the 10 initial compounds were selected and their influence was studied with a central composite design with five coded levels (Tables 3 and 4). A two-blocks design was built as follows: a 25–۱ fractional factorial design (16 cube points) augmented with one replication of the centre point (all factors at level 0) and the 11 star points having for one factor an axial distance to the centre of a, whereas the other factors were at level 0. The axial point a coded was ۲٫۲۷۵۱۹٫ A second-order polynomial equation obtained by multiple regression was used to fully describe the response surface. Then