A mutated rabbit defensin NP-1 produced by Chlorella ellipsoidea can improve the growth performance of broiler chickens.

The demand for alternatives to antibiotics to improve the growth performance of food animals is increasing. Defensins constitute the first line of defence against pathogens in the innate immune system of animals and humans. A transgenic Chlorella ellipsoidea strain producing mNP-1 (a mutated rabbit defensin NP-1) was previously obtained in our laboratory. In this study, a process for producing the transgenic strain on a large scale was developed, and the C. ellipsoidea strain producing mNP-1 was used as a feed additive to improve the health and growth performance of chickens. The volume of C. ellipsoidea producing mNP-1 can be scaled up to 10,000 L with approximately 100 g/L dry biomass, and the mNP-1 content of transgenic microalgal powder (TMP) was 90-105 mg/L. A TMP-to-regular feed ratio of 1‰, as the optimal effective dose, can promote the growth of broiler chickens by increasing weight by 9.27-12.95%. mNP-1 can improve duodenum morphology by promoting long and thin villi and affect the microbial community of the duodenum by increasing the diversity and abundance of beneficial microbes. These results suggested that transgenic Chlorella producing mNP-1 can be industrially produced and used as an effective feed additive and an alternative to antibiotics for improving the health and growth performance of broiler chickens or other types of food animals/poultry.