Isolation and Identification of a Rumen Lactobacillus Bacteria and Its Degradation Potential of Gossypol in Cottonseed Meal during Solid-State Fermentation

Effective Degradation of Free Gossypol in Defatted Cottonseed Meal by Bacterial Laccases: Performance and Toxicity Analysis

Cottonseed meal (CSM) is the major by-product of the cottonseed oil extraction process with high protein content. However, the presence of free gossypol (FG) in CSM severely restricts its utilization in the food and animal feed industries. The development of a biological strategy for the effective removal of FG in CSM has become an urgent need. In this study, three bacterial laccases including CotA from Bacillus licheniformis, CueO from Escherichia coli, and LcLac from Loigolactobacillus coryniformis were heterologously expressed and investigated for their FG degradation ability. The results showed that CotA laccase displayed the highest FG-degrading capacity among the three laccases, achieving 100% FG degradation at 37 °C and pH 7.0 in 1 h without the addition of a redox mediator. Moreover, in vitro and in vivo studies confirmed that the hepatotoxicity of FG was effectively eliminated after oxidative degradation by CotA laccase. Furthermore, the addition of CotA laccase could achieve 87% to 98% FG degradation in defatted CSM within 2 h. In conclusion, CotA laccase can be developed as an effective biocatalyst for the detoxification of FG in CSM.

The rumen-derived Lact. mucosae LLK-XR1 exhibited greater free gossypol degradation capacity during solid-state fermentation of cottonseed meal and probiotic potential

BACKGROUND

This study aimed to isolate the rumen-derived bacteria with the ability to degrade free gossypol (FG), and to evaluate the probiotic potential in vitro for ensuring safe utilization.

METHODS

The strains were anaerobically isolated from fresh rumen fluid of sheep with long-term fed cottonseed meal (CSM) with the screening agar medium containing gossypol as the sole carbon source. Afterwards, the isolated strain incubated with CSM was subjected to the determination of the FG degradation and in vitro evaluation of probiotic characteristics.

RESULTS

The target strain labeled Lact. mucosae LLK-XR1 [Accession number: OQ652016.1] was obtained, and its growth on MRS Liquid medium exhibited degradation efficiency of FG up to 69.5% which was significantly greater than its growth on Man-Rogosa-Sharpe medium with glucose free for 24 h (p < 0.01). Meanwhile, LLK-XR1 showed 40.652% degradation rate of FG for unautoclaved, non-pulverized, and no additional nutrients supplementation CSM. Furthermore, LLK-XR1 presented good survivability at pH 3.0 (above 88.6%), and 0.3% bile (78.5%). LLK-XR1 showed sensitivity to broad-spectrum antibiotics except Sulfamethoxazole, Ciprofloxacin and Gentamycin and significantly inhibited E. coli CICC 10,899, Staph. aureus CICC 21,600, and Salmonella. Typhimurium CICC 21,483. LLK-XR1 demonstrated good cell surface hydrophobicity and auto-aggregation ability.

CONCLUSIONS

Taken together, this study for the first time noted that rumen-originated Lact. mucosae LLK-XR1 with probiotic properties exhibited substantial FG degradation capacity when it was applied to the solid-state fermentation of CSM.

Biodegradation of Gossypol by Aspergillus terreus-YJ01

Gossypol, generally found in the roots, stems, leaves, and, especially, the seeds of cotton plants, is highly toxic to animals and humans, which inhibits the use of cotton stalks as a feed resource. Here, a promising fungal strain for biodegrading gossypol was successfully isolated from the soil of cotton stalk piles in Xinjiang Province, China, and identified as Aspergillus terreus-YJ01 with the analysis of ITS. Initial gossypol of 250 mg·L-1 could be removed by 97% within 96 h by YJ01, and initial gossypol of 150 mg·L-1 could also be catalyzed by 98% or 99% within 36 h by the intracellular or extracellular crude enzymes of YJ01. Sucrose and sodium nitrate were found to be the optimal carbon and nitrogen sources for the growth of YJ01, and the optimal initial pH and inoculum size for the growth of YJ01 were 6.0 and 1%, respectively. To further elucidate the mechanisms underlying gossypol biodegradation by YJ01, the draft genome of YJ01 was sequenced using Illumina HiSeq, which is 31,566,870 bp in length with a GC content of 52.27% and a total of 9737 genes. Eight genes and enzymes were predicted to be involved in gossypol biodegradation. Among them, phosphoglycerate kinase, citrate synthase, and other enzymes are related to the energy supply process. With sufficient energy, β-1, 4-endo-xylanase may achieve the purpose of biodegrading gossypol. The findings of this study provide valuable insights into both the basic research and the application of A. terreus-YJ01 in the biodegradation of gossypol in cotton stalks.

Anaerobic solid-state fermentation with Bacillus subtilis for digesting free gossypol and improving nutritional quality in cottonseed meal

Microbial fermentation is an effective method to degrade free-gossypol, which is a toxic substance restricting the utilization of cottonseed meal in animal husbandry. However, there are few researches on the nutritional effect and the change of bacterial community on cottonseed meal fermented with anaerobic solid-state fermentation. This study evaluated the effects of fermentation with Bacillus sp. on gossypol degradation and nutritional quality improvement in cottonseed meal (CM), as well as the changes of bacterial community structure during fermentation. The strains with high activity for digesting free gossypol were screened from high protease-producing strains preserved in the laboratory. Then the strains which had both the gossypol degradation activity and protease producing activity were selected to degrade macromolecular protein and free gossypol in CM. The unsterilized SSF medium was inoculated with 109 CFU/kg Bacillus culture and fermented at room temperature for 14 days. Each group had three parallels. And the effects of anaerobic solid-state fermentation on unsterilized CM was evaluated. Results showed that for the seven strains with high activity for digesting free gossypol and producing protease that were screened, free gossypol content in fermented cottonseed meal (FCM) decreased and acid-soluble protein (ASP) contents increased. Among them, strain M-15 had the best fermentation effect, with the free gossypol degradation rate of 93.46% and acid soluble protein content of 13.26%. M-15 was identified as Bacillus subtilis. During fermentation with M-15, the bacterial diversity in CM was reduced, but not significant and the community structure was simpler significantly. The strain M-15 selected in this experiment reduced the free gossypol content and improved the nutritional quality of CM through anaerobic solid-state fermentation, which can be used for industrial large-scale production.

Effective gossypol removal from cottonseed meal through optimized solid-state fermentation by Bacillus coagulans

BACKGROUND

Cottonseed meal (CSM) is the main by-product of the cottonseed oil extraction process with high protein content, which is an important protein source for feed industry. However, CSM contains free gossypol (FG), a toxic substance that is detrimental to animal health and greatly limits its application. Microbial fermentation is currently considered to be one of the most effective methods to reduce FG and other anti-nutritional factors in CSM. Previously, yeast and bacteria species are used for degradation of FG in CSM, but showing less detoxification efficiency. Bacillus coagulans combines the properties of both lactic acid bacteria and Bacillus, producing both lactic acid and spores, and is considered a potential probiotic. In this study, we aimed to evaluate and optimize the effect of the solid-state fermentation process using a Bacillus coagulans to gossypol removal contained cottonseed meal.

RESULTS

36 B. coagulans strains were isolated and found to have the ability to remove free gossypol. Through the evaluation of strains and optimization of fermentation conditions including fermentation temperature, ratio of material to water, inoculation amount, fermentation time and pH, we have established a solid-state fermentation process using a Bacillus coagulans strain S17 on CSM substrate with 1:1 of the material-to-water ratio, 15% (v/w) seed inoculation, 2% expanded corn flour, 1% bran, and 0.3%-0.8% metal irons at 40 °C for 52 h. After fermentation, the FG content in CSM was reduced from 923.80 to 167.90 mg/kg with 81.83% detoxification efficiency. Meanwhile, the crude protein content in CSM increased from 47.98 to 52.82%, and importantly, the spore concentration of strain S17 reached 1.68 × 10¹⁰ CFU/g dry material.

CONCLUSION

The study showed that B. coagulans have the potential strong ability to degrade free gossypol through cottonseed meal fermentation. This study presents a feasible process for improving the resource utilization rate and nutritional value of CSM via solid-state fermentation through B. coagulans S17.

Biodegradation of Free Gossypol by Helicoverpa armigera Carboxylesterase Expressed in Pichia pastoris

Gossypol is a polyphenolic toxic secondary metabolite derived from cotton. Free gossypol in cotton meal is remarkably harmful to animals. Furthermore, microbial degradation of gossypol produces metabolites that reduce feed quality. We adopted an enzymatic method to degrade free gossypol safely and effectively. We cloned the gene cce001a encoding carboxylesterase (CarE) into pPICZαA and transformed it into Pichia pastoris GS115. The target protein was successfully obtained, and CarE CCE001a could effectively degrade free gossypol with a degradation rate of 89%. When esterase was added, the exposed toxic groups of gossypol reacted with different amino acids and amines to form bound gossypol, generating substances with (M + H) m/z ratios of 560.15, 600.25, and 713.46. The molecular formula was C₂₇H₂₈O₁₃, C₃₄H₃₆N₂O₆, and C₄₇H₅₉N₃O₃. The observed instability of the hydroxyl groups caused the substitution and shedding of the group, forming a substance with m/z of 488.26 and molecular formula C₃₁H₃₆O₅. These properties render the CarE CCE001a a valid candidate for the detoxification of cotton meal. Furthermore, the findings help elucidate the degradation process of gossypol in vitro.

Intestinal Microbiota Mediates Gossypol-Induced Intestinal Inflammation, Oxidative Stress, and Apoptosis in Fish

Gossypol, the main antinutritional factor in cottonseed protein concentrate (CPC), could affect the growth conditions of fish, but the underlying mechanism remains unclear. In this study, an 8-week feeding trial was carried out to investigate the effects of gossypol on Nile tilapia (Oreochromis niloticus). Three experimental diets were designed, including control diet (CON), control diet supplemented with 150 mg/kg gossypol (ML), and 300 mg/kg gossypol (MH). 16S rRNA gene sequencing showed that gossypol significantly reduced the richness and diversity of the gut microbiota. Untargeted metabolite analysis revealed that most metabolites were down-regulated by gossypol, and riboflavin was the key metabolite with significant difference between CON-treated and gossypol-treated groups. Gossypol caused intestinal inflammation, oxidative stress, and apoptosis. Through fecal bacteria transplantation experiments, we demonstrated that intestinal microbiota mediated gossypol-induced negative effects, suggesting that intestinal microbiota and its metabolite may account for the harmful effects of gossypol.

High-Gossypol Whole Cottonseed Exhibited Mediocre Rumen Degradability and Less Microbial Fermentation Efficiency than Cottonseed Hull and Cottonseed Meal with an In Vitro Gas Production Technique

To explore whether or not the gossypol varied in cottonseed by-products affect rumen degradability and fermentation efficiency, an in vitro cumulative gas production experiment was applied with mixed rumen microorganism to compare rumen fermentation characteristics of whole cottonseed (WCS, n = 3 samples), cottonseed meal (CSM, n = 3 samples), and cottonseed hull (CSH, n = 2 samples). The five-replicate fermentation per sample per incubation time continuously lasted for 0.5, 1.5, 3, 6, 12, 24, 36, and 48 h with an automated gas production recording system. Regardless of distinct nutrient differences, the free gossypol level in these cottonseed by-products ranked: WCS > CSH > CSM. After 48 h of incubation, the in vitro dry matter degradability and ammonia N concentration ranked as: CSM > WCS > CSH. The cumulative gas production and total volatile fatty acid (VFA) levels in the culture fluids ranked: CSM > CSH > WCS, in which the average production rate ranked: CSM > WCS > CSH. Regarding the molar VFA pattern, WCS in comparison with CSH and CSM presented the lowest production of non-glucogenic acids (e.g., acetate) and exhibited the highest fermentation efficiency of energy from carbohydrates to VFAs. There was a significant negative correlation between the gossypol content and cumulative gas and total VFA production, suggesting that the greater gossypol in cottonseed by-products, the more detrimental effect occurred for rumen fermentation. In a brief, WCS exhibited mediocre rumen degradability and less microbial fermentation efficiency than CSH and CSM, depending on their gossypol levels.