Abstract
Antimicrobial peptides (AMPs) are short and positively charged peptides with broad-spectrum antimicrobial activities. AMPs have been investigated as potential antibiotic alternatives to improve growth performance and prevent pathogen infection in the poultry industry. The antimicrobial peptide tilapia piscidin 4 (TP4) was derived from Oreochromis niloticus, possesses antimicrobial activities and immunomodulatory properties, promotes intestinal health, and protects against pathogen infection. The codon-optimized sequence of TP4 was introduced into the pPICZαA vector and transformed into Pichia pastoris. Large-scale expression was induced following culture with methanol in a 500-liter fermenter. Freeze drying of fermented rTP4 broth and then rTP4 evaluation as a feed additive for Gallus gallus domesticus were performed. The in vitro antimicrobial activity of recombinant TP4 (rTP4) against gram-positive and gram-negative pathogens was evaluated. Evaluation of the effect of temperature on the antimicrobial activity of rTP4 showed its high stability at high temperatures. rTP4 significantly enhanced the phagocytic activity of macrophage cells, indicating that rTP4 has a remarkable ability to stimulate macrophages. rTP4 was used as a dietary supplement at 0.75, 1.5, 3.0, 6.0 and 12% in G. g. domesticus for five weeks, and growth performance, gut microbiota composition, and histology were assessed. The 3.0% rTP4 supplement group showed a significant increase in weight gain ratio and feed efficiency compared to those of the basal broiler diet group. Crude rTP4 was expressed by yeast to significantly promote growth efficiency and resistance against pathogens in G. g. domesticus, which could indicate its use as a suitable alternative to antibiotics as feed additives in the poultry industry.
Highlights
Antibiotics are commonly used to prevent disease and promote growth in agriculture
The pPICZαA plasmid ligated with tilapia piscidin 4 (TP4) was digested with PmeI within the AOX1 region to linearize the pPICZαA vector, and TP4 genes were transformed into the Pichia pastoris X-33 strain
Transformed P. pastoris X-33 colonies integrated with recombinant pPICZαA-TP4 DNA were selected by colony hybridization by using an anti-6xHis tag antibody, and high-expression clones were picked for subsequent experiments
Summary
Antibiotics are commonly used to prevent disease and promote growth in agriculture. For poultry and livestock production, antibiotics are often used to treat clinical diseases and to control and prevent common infections. While antibiotics are used in animals for growth promotion or increased feed efficiency [1], the low concentration of antibiotics to which bacteria are exposed for a long period of time is problematic. Antibiotics have been used in poultry production as therapeutic agents to treat and control necrotic enteritis and respiratory diseases and to improve feed conversion and body weight gain [2]. These effects are due mainly to antibiotic treatment-induced gut microbiota alteration and microbiota modification in the gastrointestinal tract to provide an optimal microbiota for growth [3]. Unlimited use of antibiotics will lead to reduced therapeutic effectiveness and generate many drug-resistant strains that may have negative effects on animal and human health [4]
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