ObjectiveThe aim of the study was to isolate gossypol-degrading bacteria and to assess its potential for gossypol degradation.MethodsRumen liquid was collected from fistulated cows grazing the experimental pasture. Approximately 1 mL of the rumen liquid was spread onto basal medium plates containing 2 g/L gossypol as the only source of carbon and was then cultured at 39°C to isolate gossypol-degrading bacteria. The isolated colonies were cultured for 6 h and then their size and shape observed by microscope and scanning electron microscope. The 16S rRNA gene of isolated colonies was sequenced and aligned using National Center for Biotechnology Information-Basic Local Alignment Search Tool. The various fermentation conditions, initial pH, incubation temperature, inoculum level and fermentationperiod were analyzed in cottonseed meal (CSM). The crude protein (CP), total gossypol (TG), and free gossypol (FG) were determined in CSM after fermentation with isolated strain at 39°C for 72 h.ResultsScreening results showed that a single bacterial isolate, named Rumen Bacillus Subtilis (RBS), could use gossypol as a carbon source. The bacterium was identified by 16S rDNA sequencing as being 98% homologous to the sequence of Bacillus subtilis strain GH38. The optimum fermentation conditions were found to be 72 h, 39°C, pH 6.5, moisture 50%, inoculum level 107 cell/g. In the optimum fermentation conditions, the FG and TG content in fermented CSM decreased 78.86% and 49% relative to the control. The content of CP and the essential amino acids of the fermented CSM increased respectively, compared with the control.ConclusionThe isolation of a gossypol-degrading bacterium from the cow rumen is of great importance for gossypol biodegradation and may be a valuable potential source for gossypol-degradation of CSM.

This study was performed to evaluate effects of Armillariella tabescens (A. tabescens) on the growth performance and intestinal immune response and microflora in early-weaned pigs when used as feed additive. A. tabescens mycelia were added to basal diets at concentrations of 0%, 0.1%, 0.3% or 0.9% (w/w). A total of 144 commercial cross-bred piglets were randomly allocated to one of these four diets and fed for 30 days. The growth performance of early-weaned piglets displayed improvement with diets containing 0.1% and 0.3% dried mycelia powder from A. tabescens. Supplementing with 0.1% or 0.3% A. tabescens mycelia induced a 2.6- and three-fold increase in secretory immunoglobulin A (sIgA) content in the jejunal mucosa, respectively, but had only a marginal effect on sIgA in the ileal mucosa. Expression of interleukin-2, interferon-γ, and tumor necrosis factor-α in the jejunal mucosa were elevated with A. tabescens mycelia administration. Increased amounts of Lactobacillus spp. and Bifidobacterium spp. in the jejunum, and decreased amounts of Escherichia coli in the jejunum and ileum were observed with the administration of A. tabescens-containing diets. This study demonstrated that A. tabescens had beneficial effects on the growth performance and intestinal microflora of early-weaned pigs.

Background The gossypol, as an antinutritional factor or natural plant toxin, has antifertility effects on humans and animals, exists in cottonseed oil and meal, and is a typical food or feed contaminant. It is the classic screening method to using acetate gossypol as the sole carbon sources to prepare selective medium and screening gossypol-degrading microorganisms. By the classic screening strategy, many researchers have discovered that some microorganisms, and Aspergillus niger is the most reported microorganism. A strain of A. niger which can grow in an agar solid medium with gossypol as the sole carbon source is isolated from cattle rumen liquid was obtained by classic screening strategy. The effectiveness of the classic screening strategy was verified, by duplicating and verifying the degradation of gossypol by the A. niger. Results the A. niger can reduce the free gossypol (FG) content through biosorption but has no effect on the total gossypol (TG) content. And it can secrete agarase, utilise agar as carbon source. Conclusions The A. niger can secrete agarase, but cannot effectively degrade gossypol, In this case, it will mislead researchers and lead them to make wrong judgments. The usual methods of previous screening strategies are not rigorous enough, the classic screening method has defect in screening toxin-degrading strain, so agar control group should be added.

The effectiveness of the classic screening strategy was verified, by duplicating and verifying the degradation of gossypol by the Aspergillus niger. It can reduce the free gossypol content through biosorption but has no effect on the total gossypol content and cannot effectively degrade gossypol. And the most interesting thing we found the strain can secrete agarase, utilise agar as carbon source. In this case, that will mislead researchers and lead them to make wrong judgments. That turns out the usual methods of previous screening strategies are not rigorous enough, the classic screening method has defect in screening toxin-degrading strain, so agar control group should be added. In this study, some suggestions are put forward to optimise the same type of experiments and broaden the idea of detoxification by microorganisms and provide reference for screening effective toxin-degrading microorganisms.