# Enzymatic Preparation of Carrageenan Oligosaccharides and Evaluation of the Effects on Growth Performance, Serum Biochemical Parameters and Non-Specific Immunity of Crucian carp

## TL;DR

This study shows that adding carrageenan oligosaccharides to the diet of crucian carp improves their growth and immunity.

## Contribution

A novel carrageenase CgkA was used to prepare COSs, and their effects on fish immunity and growth were experimentally evaluated.

## Key findings

- COSs improved growth performance and survival ratio in crucian carp.
- COSs reduced oxidative stress and enhanced immune-related enzyme activities.
- Dietary COSs increased resistance to diseases in fish.

## Abstract

Carrageenan oligosaccharides (COSs) possess versatile activities and have drawn increasing attention in recent years. Due to their unique structures, COSs have been considered to be potential antibacterial agents and immune stimulators. Herein, we aimed to efficiently prepare the COSs by using a novel carrageenase CgkA from Zobellia uliginosa with high activity and further investigate the effects of dietary supplementation with COSs on the growth performance, serum biochemical parameters and non-specific immunity in Carassius auratus gibelio. The results indicated that the CgkA could effectively degrade the carrageenan into oligosaccharides with DPs of 2–6 and the oligosaccharides exhibited promoting effects on growth performance, serum biochemical index and non-specific immune parameters. After a 6-month feeding trial, the SR (Survival Ratio) was significantly higher in fish fed 0.1% (Diet 1), 0.2% (Diet 2), 0.5% (Diet 3) and 1% (Diet 4) COSs diets than that in the control group (p < 0.05). In addition, the supplementation of COSs decreased the malondialdehyde (MDA) content in the serum and increased the activity of lysozyme (LZM), superoxide dismutase (SOD) and catalase (CAT). In conclusion, COSs as a dietary supplement enhance the growth performance and non-specific immunity of crucian carp and their resistance to diseases.