فایل ورد کامل بهینه سازی تولید فیتاز خارج سلولی از باسیلوس amyloliquefaciens PFB-02 رشد کرده بر روی ضایعات کشاورزی منتخب

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تعداد صفحات این فایل: ۱۴ صفحه

بخشی از مقاله انگلیسیعنوان انگلیسی:Optimization of Extracellular Phytase Production from Bacillus amyloliquefaciens PFB-02 Grown on Selected Agricultural Wastes~~en~~

Abstract

The undigested phytic acid excreted in animal waste causes phosphorus pollution from agriculture. Addition of microbial phytases to animal feeds is a promising approach to overcoming challenges posed by phytic acid. In this study, influence of physicochemical parameters on growth and production of phytase from Bacillus amyloliquefaciens PFB-02 was investigated over 96 h cultivation period. Effects of some readily available and low cost agricultural wastes on phytase production from B. amyloliquefaciens PFB-02 were also investigated. Maximum growth with phytase yield of 5.3 U/ml was achieved in the basal medium at 48 h cultivation period, pH 5.0, 40 °C and 180 rpm. The optimized conditions were used to study phytase production from B. amyloliquefaciens PFB-02 grown on wheat bran, black-eyed bean skin and rice bran based media under submerged fermentation conditions. Remarkably, wheat bran supported highest enzyme yield of 17.0 U/ml with 317.5% increase over yield in basal media. Rice bran and black-eyed bean skin also supported phytase production from B. amyloliquefaciens PFB-02 with yield of 4.6 U/ml and 3.5 U/ml, respectively. The results suggest that agricultural wastes are effective low cost substrates for phytase production from B. amyloliquefaciens PFB-02 for potential application in animal feed formulation.

۱ Introduction

Phytase (myo-inositol (1,2,3,4,5,6) hexakisphosphate phosphohydrolase catalyzes the hydrolysis of phytic acid (myo-inositol hexakisphosphate) to inorganic phosphate and myoinositol phosphate derivatives (Wyss et al., 1999). Phytic acid, the storage form of phosphorus in many cereals and legumes fed to animals has negative impact on animal nutrition and environment (Raboy, 2007).

Ruminants digest phytic acid by phytases from fungi and bacteria present in their gut microflora. However, phytic acid is poorly digested by monogastric animals which lack sufficient phytase in their digestive tracts. The undigested phytic acid is excreted in animal waste and has been reported as a major source of phosphorus pollution from agriculture (Raboy, 2007). Furthermore, the reduced bioavailability of essential mineral cations to animals results from the tight binding of phosphate in phytic acid to Ca2+ , Fe3+ , K + , Mg2+ , Mn2+ and Zn2+ (Bohn et al., 2008; Ravindran et al., 1995; Torre et al., 1991). Phytic acid has been reported to have negative impact on amino acid digestibility thus making it a limiting factor on protein availability (Selle et al., 2006). In fact, protein-phytate interactions are fundamental to the detrimental impact of phytate on protein/amino acid availability in pig and poultry nutrition (Selle et al., 2012).

A promising approach to overcoming these challenges posed by phytic acid is based on addition of microbial phytases to animal feeds as supplements to improve digestibility and dietary phytate-phosphorus utilization (Liao et al., 2005; Stahl et al., 2004;). Consequently, phytases have become important industrial enzymes and presently, there is continuous search for phytases from different microbial sources which have potentials for industrial use. The major challenge in this approach is the cost of microbial phytase production which could be a barrier to their utilization. Hence, there is an urgent need to screen for phytase production from variety of microbial sources and investigate conditions that support high yield of the enzyme at very low cost. Reduction in the production cost of microbial phytases could greatly reduce the cost of the enzyme for use as supplements in animal feeds. Efficient, scalable and economical process for improved yield of phytase production is critically required (Bhavsar and Khire, 2014).

Consequently, this study investigated the production of phytase from Bacillus amyloliquefasciens PFB-02 and optimization of the enzyme yield using inexpensive and readily available agricultural wastes at predefined conditions.

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