Isolation and characterization of a novel gossypol-degrading bacteria Bacillus subtilis strain Rumen Bacillus Subtilis

Abstract

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.

Cottonseed Press Cake as a Potential Diet for Industrially Farmed Black Soldier Fly Larvae Triggers Adaptations of Their Bacterial and Fungal Gut Microbiota

“…Other families present only in larvae reared on CPC ( Burkholderiaceae , Rhizobiaceae , Erysipelotrichaceae , and Clostridiales Family XI) may also be involved in the degradation of such compounds, but little is known about gossypol degradation in bacteria. The only gossypol-degrading bacterial isolate known thus far is a Bacillus subtilis strain isolated from the cow rumen, but this is not yet available in a culture collection ( Zhang et al, 2018 ).…”

“…Accordingly, CPC is generally unsuitable as feed because it causes growth depression, infertility and disorders of digestion ( Herman, 1970 ; Berardi and Goldblatt, 1980 ; Liener et al, 1990 ; Francis et al, 2001 ). Thus far, only ruminants have been shown to tolerate CPC because they produce rumen proteins that detoxify gossypol by sequestration into inactive complexes ( Reiser and Fu, 1962 ) prior to degradation by microbes, which use the gossypol as a carbon source ( Zhang et al, 2018 ). Reflecting this microbial activity, fermented cottonseed meal therefore has lower levels of bound and free gossypol and is enriched with vitamins and enzymes ( Zhang et al, 2006 , 2007 ; Khalaf and Meleigy, 2008 ; Lim et al, 2010 ; Mageshwaran et al, 2017 ).…”

Effectiveness of the toxin-degrading strain screening strategy: Deficiency and improvement in screening the gossypol-degrading microorganism Aspergillus niger

“…The gossypol exists in cottonseed oil and meal (CM), and is a typical food or feed contaminant [9]. Through the classic screening method, many researchers have discovered that some microorganisms, such as Aspergillus niger (AN) [10], Candida tropicalis [11], Aspergillus avus [12] and Bacillus subtilis [13], can degrade gossypol, and AN is the most reported microorganism. On the basis of previous screening strategies, AN that can grow in an agar solid medium with gossypol as the sole carbon source is isolated from cattle rumen liquid.…”

Effect of dietary gossypol supplement on fermentation characteristics and bacterial diversity in the rumen of sheep

“…One explanation is that the free gossypol can be converted into bound gossypol by binding to soluble proteins [12]. The other is that gossypol can be used as a carbon source by rumen microorganisms, assuming that gossypol is degraded into nontoxic metabolites [13].…”