Effects of Clostridium tyrobutyricum on Lipid Metabolism, Intestinal Barrier Function, and Gut Microbiota in Obese Mice Induced by High-Fat Diet

Obesity and its complications constitute a main threat to global human health. The purpose of this investigation was to explore the influences of Clostridium tyrobutyricum (Ct) on lipid metabolism, intestinal barrier function, and intestinal microbiome in obese mice induced by a high-fat diet (HFD). After establishing the obesity model, 107 CFU/mL and 108 CFU/mL C. tyrobutyricum were used to intervene in HFD-fed mice by gavage for six weeks, and indexes related to obesity were measured. In the liver of HFD-fed mice, the results revealed that C. tyrobutyricum reduced liver weight and the levels of triglyceride (TG), total cholesterol (TC), and nonesterified fatty acid (NEFA), along with decreasing red lipid droplets and fat vacuoles. After C. tyrobutyricum intervention, the mRNA expression of peroxisome proliferator-activated receptor-γ (PPARγ) was downregulated, and AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor-α (PPARα), adipose triglyceride lipase (ATGL), and hormone-sensitive lipase (HSL) were upregulated in the liver. Additionally, C. tyrobutyricum alleviated intestinal morphology injury caused by HFD, decreased the expression of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), and IL-1β in the colon, and upregulated tight junction protein expression. In addition, 16S rRNA sequencing revealed that C. tyrobutyricum increases the diversity of intestinal microbiota. Overall, C. tyrobutyricum improved HFD-induced lipid metabolism disorders, preserved the intestinal barrier's integrity, and modulated the structure of the intestinal microbiome. These findings provide a novel insight into the role of C. tyrobutyricum as a probiotic in regulating lipid metabolism.

Clostridium butyricum and Clostridium tyrobutyricum: angel or devil for necrotizing enterocolitis?

IMPORTANCE

This study sheds light on that treatment with Clostridium tyrobutyricum but not Clostridium butyricum is entitled to protect against necrotizing enterocolitis (NEC) development potentially. The mechanisms behind the opposite effect on NEC may result in different modulation on the level of Akkermansia muciniphila, which is deeply associated with intestinal homoeostasis. Briefly, through improving the abundance of A. muciniphila to alleviate intestinal inflammation and enhance intestinal barrier integrity, C. tyrobutyricum supplement may become a promising therapy for NEC.

Butanol production from Saccharina japonica hydrolysate by engineered Clostridium tyrobutyricum: The effects of pretreatment method and heat shock protein overexpression

Macroalgal biomass is currently considered as a potential candidate for biofuel production. In this study, the effects of pretreatment method and heat shock protein overexpression were investigated for efficient butanol production from Saccharina japonica using engineered Clostridium tyrobutyricum. First, various pretreatment methods including acid hydrolysis, acid hydrolysis and enzymatic saccharification, and ultrasonic-assisted acid hydrolysis were employed to obtain the fermentable sugars, and the resulted hydrolysates were evaluated for butanol fermentation. The results showed that ultrasonic-assisted acid hydrolysate obtained the highest butanol yield (0.26 g/g) and productivity (0.19 g/L⋅h). Then, the effects of homologous or heterologous heat shock protein overexpression on butanol production and tolerance were examined. Among all the engineered strains, Ct-pMA12G exhibited improved butanol tolerance and enhanced butanol production (12.15 g/L butanol with a yield of 0.34 g/g and productivity of 0.15 g/L⋅h) from 1.8-fold concentrated S. japonica hydrolysate, which was the highest level ever reported for macroalgal biomass.

Metal-organic frameworks coupling simultaneous saccharication and fermentation for enhanced butyric acid production from rice straw under visible light by Clostridium tyrobutyricum CtΔack::cat1

Here, Metal-Organic Frameworks (MOFs) coupling simultaneous saccharification and fermentation for butyric acid production using rice straw was constructed. Clostridium tyrobutyricum Δack::cat1, with deleted ack gene and overexpressed cat1 gene, was used as the butyric-acid-fermentation strain. MOFs was employed as a photocatalyst to improve butyric acid production, as well as a cytoprotective exoskeleton with immobilized cellulase for the hydrolysis of rice straw. Thus, the survival of MOFs-coated strain, the thermostability and pH stability of cellulase both remarkably increased. As a result, 55% of rice straw was hydrolyzed in 24 h, and the final concentration of butyric acid in visible light was increased by 14.23% and 29.16% compared to uncoated and coated strain without visible light, respectively. Finally, 26.25 g/L of butyric acid with a productivity of 0.41 g/L·h in fed-batch fermentation was obtained. This novel process inspires green approach of abundant low-cost feedstocks utilization for chemical production.

Butyric acid production from spent coffee grounds by engineered Clostridium tyrobutyricum overexpressing galactose catabolism genes

Clostridium tyrobutyricum cannot utilize galactose, which is abundant in lignocellulose and red algae, as a carbon source for butyric acid production. Hence, when using galactose-rich coffee ground hydrolysate as the substrate, the fermentation performance of C. tyrobutyricum is poor. In this work, a recombinant strain, C. tyrobutyricum ATCC 25755/ketp, overexpressing galactose catabolism genes (galK, galE, galT, and galP) from Clostridium acetobutylicum ATCC 824 was constructed for the co-utilization of glucose and galactose. Batch fermentation in the bioreactor showed that ATCC 25755/ketp could efficiently utilize galactose without glucose-induced carbon catabolite repression and consume nearly 100% of the galactose present in the spent coffee ground hydrolysate. Correspondingly, the butyric acid concentration and productivity of ATCC 25755/ketp reached 34.3 g/L and 0.36 g/L·h, respectively, an increase of 78.6% and 56.5% compared with the wild-type strain, indicating its potential for butyric acid production from hydrolysates of inexpensive and galactose-rich biomass.

Direct conversion of untreated cane molasses into butyric acid by engineered Clostridium tyrobutyricum

The sucrose metabolic genes (scrA, scrB and scrK) from C. acetobutylicum ATCC 824 were successfully overexpressed in C. tyrobutyricum ATCC 25755, endowing it with the ability to co-utilize sucrose, fructose and glucose in the cane molasses. As a result, the engineering strain C. tyrobutyricum ATCC 25755/scrBAK produced 18.07 g/L and 18.98 g/L butyric acid when sucrose and cane molasses were used as the carbon source, respectively. Furthermore, the medium composition and initial cane molasses concentration were optimized to make full use of the untreated cane molasses. Based on these results, 45.71 g/L butyric acid with a yield of 0.39 g/g was obtained in fed-batch fermentation, and the feedstock cost of using untreated cane molasses was decreased by ~47% when compared with the conventional glucose fermentation. This study demonstrated the potential application of C. tyrobutyricum ATCC 25755/scrBAK for economic butyric acid production from untreated cane molasses.

Co-valorization of paper mill sludge and corn steep liquor for enhanced n-butanol production with Clostridium tyrobutyricum Δcat1::adhE2

In this study, hyper-butanol producing Clostridium tyrobutyricum Δcat1::adhE2 was used for butanol production from paper mill sludge (PMS) and corn steep liquor (CSL). Our results demonstrated that CSL can not only serve as a cheap nitrogen source, but also provide lactic acid that can be assimilated by C. tyrobutyricum for enhanced butanol production. Through a separate hydrolysis and fermentation, 16.5 g/L butanol with a yield of 0.26 g/g was obtained from PMS hydrolysates supplemented with 5% CSL. Further, a separate repeated hydrolysis was conducted to improve PMS hydrolysis rate and enhance sugar yield. Fermentation using hydrolysates from such process also generated high-level butanol with high yield. Our results suggested an innovative bioprocess for efficient biobutanol production from low-value waste streams.

Production of n-butanol from cassava bagasse hydrolysate by engineered Clostridium tyrobutyricum overexpressing adhE2: Kinetics and cost analysis

The production of biofuels such as butanol is usually limited by the availability of inexpensive raw materials and high substrate cost. Using food crops as feedstock in the biorefinery industry has been criticized for its competition with food supply, causing food shortage and increased food prices. In this study, cassava bagasse as an abundant, renewable, and inexpensive byproduct from the cassava starch industry was used for n-butanol production. Cassava bagasse hydrolysate containing mainly glucose was obtained after treatments with dilute acid and enzymes (glucoamylases and cellulases) and then supplemented with corn steep liquor for use as substrate in repeated-batch fermentation with engineered Clostridium tyrobutyricum CtΔack-adhE2 in a fibrous-bed bioreactor. Stable butanol production with high titer (>15.0 g/L), yield (>0.30 g/g), and productivity (~0.3 g/L∙h) was achieved, demonstrating the feasibility of an economically competitive process for n-butanol production from cassava bagasse for industrial application.

Bioaugmentation with Clostridium tyrobutyricum to improve butyric acid production through direct rice straw bioconversion

One-pot bioconversion is an economically attractive biorefinery strategy to reduce enzyme consumption. Direct conversion of lignocellulosic biomass for butyric acid production is still challenging because of competition among microorganisms. In a consolidated hydrolysis/fermentation bioprocessing (CBP) the microbial structure may eventually prefer the production of caproic acid rather than butyric acid production. This paper presents a new bioaugmentation approach for high butyric acid production from rice straw. By dosing 0.03 g/L of Clostridium tyrobutyricum ATCC 25755 in the CBP, an increase of 226% higher butyric acid was yielded. The selectivity and concentration also increased to 60.7% and 18.05 g/L, respectively. DNA-sequencing confirmed the shift of bacterial community in the augmented CBP. Butyric acid producer was enriched in the bioaugmented bacterial community and the bacteria related to long chain acids production was degenerated. The findings may be useful in future research and process design to enhance productivity of desired bio-products.

Recent advances and strategies in process and strain engineering for the production of butyric acid by microbial fermentation

Butyric acid is an important platform chemical, which is widely used in the fields of food, pharmaceutical, energy, etc. Microbial fermentation as an alternative approach for butyric acid production is attracting great attention as it is an environmentally friendly bioprocessing. However, traditional fermentative butyric acid production is still not economically competitive compared to chemical synthesis route, due to the low titer, low productivity, and high production cost. Therefore, reduction of butyric acid production cost by utilization of alternative inexpensive feedstock, and improvement of butyric acid production and productivity has become an important target. Recently, several advanced strategies have been developed for enhanced butyric acid production, including bioprocess techniques and metabolic engineering methods. This review provides an overview of advances and strategies in process and strain engineering for butyric acid production by microbial fermentation. Additionally, future perspectives on improvement of butyric acid production are also proposed.

Butyric acid production from lignocellulosic biomass hydrolysates by engineered Clostridium tyrobutyricum overexpressing Class I heat shock protein GroESL

Lignocellulosic biomass is the most abundant and renewable substrate for biological fermentation, but the inhibitors present in the lignocellulosic hydrolysates could severely inhibit the cell growth and productivity of industrial strains. This study confirmed that overexpressing of native groESL in Clostridium tyrobutyricum could significantly improve its tolerance to lignocellulosic hydrolysate-derived inhibitors, especially for phenolic compounds. Consequently, ATCC 25755/groESL showed a better performance in butyric acid fermentation with hydrolysates of corn cob, corn straw, rice straw, wheat straw, soybean hull and soybean straw, respectively. When corn straw and rice straw hydrolysates, which showed strong toxicity to C. tyrobutyricum, were used as the substrates, 29.6 g/L and 30.1 g/L butyric acid were obtained in batch fermentation, increased by 26.5% and 19.4% as compared with the wild-type strain, respectively. And more importantly, the butyric acid productivity reached 0.31 g/L·h (vs. 0.20-0.21 g/L·h for the wild-type strain) due to the shortened lag phase.

Antimicrobial potential of four Lactobacillus strains isolated from breast milk

AIMS

The antimicrobial potential of four lactobacilli (Lactobacillus salivarius CECT5713, Lactobacillus gasseri CECT5714, L. gasseri CECT5715 and Lactobacillus fermentum CECT5716), isolated from fresh human breast milk, was evaluated in this study and compared with Lactobacillus coryniformis CECT5711, a reuterin-producing strain isolated from an artisan goat's cheese.

METHODS AND RESULTS

Agar diffusion tests, competitive adhesion assays and mucin expression assays were carried out in order to value the antibacterial properties of the lactobacilli strains. The antibacterial capability of the strains was tested in vivo by using a murine infection model with Salmonella choleraesuis. The results revealed that all the strains studied, displayed antibacterial properties against pathogenic bacteria. However, the antibacterial potential varied among the lactobacilli tested and, in fact, L. salivarius CECT5713 showed not only the best in vitro antibacterial activity, but also the highest protective effect against a Salmonella strain in the murine infection model.

CONCLUSION

The four breast-milk lactobacilli, and particularly L. salivarius CECT5713, possess potent antibacterial activities that result in a higher protection against S. choleraesuis CECT4155 in a mouse infection model.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results suggest that lactobacilli from breast milk could contribute to an anti-infective protection in neonates and would be excellent candidates for the development of infant probiotic products.