A Study on the Reduction of Gossypol Levels by Mixed Culture Solid Substrate Fermentation of Cottonseed Meal

Wenju Zhang,Jianyi Sun,Xia Yang,Zirong Xu

doi:10.5713/ajas.2006.1314

Abstract

The objective of this work was to study the effect of mixed culture solid substrate fermentation of C. tropicalis ZD-3 with A. niger ZD-8 on detoxification of cottonseed meal (CSM), and to investigate the effect of fermentation period, proportion of CSM in substrate, sodium carbonate, minerals and heat treatment on the reduction of free gossypol levels during mixed culture solid substrate fermentation of CSM. Experiment 1: Three groups of disinfected CSM substrate were incubated for 48 h after inoculation with either of the fungi C. tropicalis ZD-3, A. niger ZD-8 or mixed culture (C. tropicalis ZD-3 with A. niger ZD-8). One non-inoculated group was used as the control. Levels of initial and final free gossypol (FG), CP and in vitro CP digestibility were assayed. The results indicated that mixed culture fermentation was far more effective than single strain fermentation, which not only had higher detoxification rate, but also had higher CP content and in vitro digestibility. Experiment 2: CSM substrates were treated according to experimental variables including fermentation period, proportion of CSM in substrate, sodium carbonate, minerals and heat treatment, Then, the treated CSM substrates were inoculated with mixed culture (C. tropicalis ZD-3 with A. niger ZD-8) and incubated at 30°C for 36 h in a 95% relative humidity chamber. After fermentation ended, FG and CP content of fermented CSM substrate was assayed. The results showed that the appropriate fermentation period was 36 h, and the optimal proportion of CSM in substrate was 70%. Addition of sodium carbonate to CSM substrate was beneficial for fermentative detoxification. Heat treatment could facilitate fermentative detoxification, and

Highlights

Gossypol, produced in the seeds of the cotton plant, is a naturally occurring toxin that deters insect pests
Effect of cottonseed meal (CSM) substrate fermented by C. tropicalis ZD-3 or /with A. niger ZD-8
Three groups of disinfected CSM substrate were incubated at 30°C for 48 h after inoculation with either of the fungi C. tropicalis ZD-3, A. niger ZD-8 or mixed culture (C. tropicalis ZD-3 with A. niger ZD-8)

Summary

Introduction

Gossypol, produced in the seeds of the cotton plant, is a naturally occurring toxin that deters insect pests. Feeding diets containing gossypol to animals would cause negative effects such as growth depression, reproductive disease and intestinal and other internal organ abnormalities (Berardi and Goldblatt, 1980; Francis et al, 2001; Robinson et al, 2001). Feeding gossypol to laboratory rodents would result in irregular estrous cycles and reducing pregnancy rates (Hahn et al, 1981; Lagerlof et al, 1985; Bender et al, 1988). Eisele (1986) reported that feeding sows and gilts diets containing 0.02% and 0.136% free gossypol (FG) had reduced conception rates by 72% and 77%, respectively, and failed to conceive; of those sows and gilts that did conceive, many aborted, produced stillborn piglets.

Objectives

Methods

Results