دانلود رایگان ترجمه مقاله بهینه سازی تولید فیتاز توسط جدایه باسیلوس سوبتیلیس (سال2015)

بهینه سازی تولید فیتاز توسط جدایه جدید باسیلوس سوبتیلیس. سوش EBD 9-1 با استفاده از طراحی آزمایشی آماری

Optimization of Phytase Production by New Isolate Bacillus sp. EBD 9-1 Strain using Statistical Experimental Design

Abstract

In this study, face centered central composite design (FCCCD) of response surface methodology (RSM) was applied to describe the relationship between the tested variables, pH, temperature, rpm, incubation period and phytase production by novel isolate Bacillus sp. EBD 9-1. The design was employed by selecting pH, temperature, rpm and incubation period as the model factors and to achieve maximum yield, interaction of these factors was studied by RSM. A second order quadratic model and response surface method showed that the optimum conditions for phytase production were pH, 8.0; temperature, 38.13°C; rpm, 113.64 and incubation period, 45 h. Under these conditions, phytase activity was found to be about 228 Uml-1.

1 Introduction

The main part of feedstuffs for poultry is derived from plants such as wheat, corn, and rye. Up to 80% of the grain phosphorus is bound in the phytic acid whose salt form, phytate, (Uhling 1998). The organically bound phosphate of phytic acid is not metabolized by monogastric animals such as pig, poultry and fish due to lack of phytase and consequently contributes to the phosphorus pollution problems in areas of intensive livestock production (Adeola 1999,Common 1989,Wodzinski 1996). And also, phytate is an antinutrient constituent in plant-derived food and feed, since it form complexes with proteins, amino acids (Pallauf 1997) and variety of metal ions such as calcium, magnesium, iron and zinc. Because of these problems, there is considerable interest in phytate degrading enzyme. This significant problems can be eliminated by hydrolysis of phytate using phytase (Simell et al. 1989). And thus, the phosphorus of phytate can be resorbed by the animal after hdyrolysis to inositol and inorganic phosphate. Phytases have been one of the focal enzymes for nutrition, environmental protection, and human health during the past two decades (Uhling 1998). Phytases (E.C.3.1.3.8. inositol hexaphosphate phosphohydrolase) sequentially cleave orthophosphate groups from the inositol core of phytate or phytic acid, the major chemical form (60–90%) of phosphorus in plants. These enzymes have been isolated from fungi, yeast, bacteria and protozoa (Lei et al. 2007) Bacterial phytases and phytase- producing bacteria is as well as their potential biotechnological applications. Especially, Bacillus sp., E.coli, Pseudomonas sp., Citrobacter sp., are the best alternative to produce the enzyme (Jorquera M 2008). Bacillus phytases have been studied extensively because of the immense potential of these enzymes having unique characteristics, feasibility of mass production for market and applicability in animal feed (Rao et al. 2008). Hence phytase has a great industrial significance, and there is an ongoing interest in isolation of new microbial strain producing phytase and optimization of this enzyme (Lan et al. 2002). Phytase has been marketed as a feed additive in the US since 1996 and by the close of the twentieth century annual sales of phytase, as animal feed additive, was about US$ 500 million (Vats and Banerjee 2004). This enzyme has, therefore, potential applications in feed and food industries (Singh and Satyanarayana 2010).

Response surface methodology (RSM) in biotechnological process is gaining excellent importance for optimization of enzymes production (Dahiya et al. 2009). RSM, which includes factorial designs and regression analysis, helps in evaluating the effective factors and building models to determine interaction and select optimum conditions of variables for a desirable response (Cotârlet and Bahrim 2011). Compared with conventional methods for optimization, RSM is a time- and labor-saving method, which consists mainly of the Central Composite Design (CCD), the Box Behnken Design (BBD). RSM has been used successfully for production optimization of many products, including enzyme, antibiotics and biofuel (Zhong et al. 2014). Series of experiments were carried out to determine critical variables level affecting enzymes production in this paper. Besides RSM have been used to optimize parameters (pH, temperature, rpm and incubation period) for phytase production by new isolate Bacillus sp. EBD 9-1 in the present study.