# Optimized Solid-State Fermentation of Sugar Beet Pulp with Mixed Microbes Improves Its Nutritional Value and Promotes Growth, Health, and Intestinal Function in Yellow Catfish (Pelteobagrus fulvidraco)

## TL;DR

Fermenting sugar beet pulp with specific microbes improves its nutritional value and benefits the growth, health, and gut function of yellow catfish.

## Contribution

Optimized solid-state fermentation of sugar beet pulp with a specific microbial mix enhances its use as a sustainable aquafeed.

## Key findings

- Fermented sugar beet pulp at 9% inclusion improved growth and muscle texture in yellow catfish.
- FBP reduced serum lipids and liver enzymes while enhancing antioxidant capacity in fish.
- FBP increased digestive enzyme activity and enriched beneficial gut bacteria like Leucobacter.

## Abstract

The rising cost of traditional feed ingredients like soybean meal is a major challenge for fish farming. This study explored a way to turn sugar beet pulp—an abundant and inexpensive by-product from sugar production—into a nutritious feed for yellow catfish. We used a special mix of helpful bacteria and yeast to ferment the pulp, which improved its protein content and reduced its tough fibers. When we replaced 9% of the soybean meal in the fish diet with this fermented pulp, the fish grew better, their muscle texture improved, and they showed signs of better overall health, including healthier livers and intestines. The fermented pulp also increased the number of beneficial bacteria in the fish gut. These results show that fermented sugar beet pulp is a promising, cost-effective feed ingredient that can support sustainable aquaculture by making good use of agricultural leftovers, lowering feed costs, and improving fish quality and welfare.

The rising cost of conventional protein sources such as soybean meal has prompted the search for sustainable and economical alternatives in aquafeeds. Sugar beet pulp (SBP), an abundant by-product of the sugar industry, possesses nutritional potential but is limited by its high fiber and anti-nutritional factors. Solid-state fermentation (SSF) offers a promising approach to enhance its nutritive value and functional properties. This study evaluated the effects of dietary inclusion of mixed microbial solid-state fermented beet pulp (FBP) on the growth, systemic health and intestinal function of juvenile yellow catfish (Pelteobagrus fulvidraco). First, orthogonal optimization determined Lactiplantibacillus plantarum:Saccharomycopsis fibuligera:Bacillus subtilis = 1:3:3 as the optimal ratio, significantly improving the nutritional profile of FBP. Based on this optimized FBP, an 8-week feeding trial, five isonitrogenous and isolipidic diets were formulated by replacing 0–12% soybean meal with FBP. The results demonstrated that 9% FBP inclusion yielded optimal growth performance and significantly improved muscle texture. At the systemic level, FBP supplementation reduced serum lipid markers and liver enzyme activities while enhancing antioxidant capacity. At the intestinal level, FBP promoted intestinal health by increasing key digestive enzyme (lipase, trypsin, amylase) activities, stimulating villus development, and improving intestinal antioxidant status. Furthermore, gut microbiota analysis revealed that dietary FBP supplementation significantly modulated intestinal microbial composition, with notable enrichment of genera such as Leucobacter. In conclusion, FBP is a multi-functional ingredient that enhances growth, product quality, systemic physiology, and intestinal health in yellow catfish aquaculture. These findings provide a viable strategy for the sustainable utilization of agricultural by-products in aquafeeds.