Fermentative hydrogen production by the newly isolated Clostridium beijerinckii Fanp3

A hydrogen producing strain newly isolated from anaerobic sludge in an anaerobic bioreactor, was identified as Clostridium beijerinckii Fanp3 by 16S rDNA gene sequence analysis and detection by BioMerieux Vitek. The strain could utilize various carbon and nitrogen sources to produce hydrogen, which indicates that it has the potential of converting renewable wastes into hydrogen. In batch cultivations, the optimal initial pH of the culture medium was between 6.47 and 6.98. Using 0.15 M phosphate as buffer could alleviate the medium acidification and improve the overall performance of C. beijerinckii Fanp3 in hydrogen production. Culture temperature of 35 °C was established to be the most favorable for maximum rate of hydrogen production. The distribution of soluble metabolic products (SMP) was also greatly affected by temperature. Considering glucose as a substrate, the activation energy (E_a) for hydrogen production was calculated as 81.01 kcal/mol and 21.4% of substrate energy was recovered in the form of hydrogen. The maximal hydrogen yield and the hydrogen production rate were obtained as 2.52 mol/mol-glucose and 39.0 ml/g-glucose h⁻¹, respectively. These results indicate that C. beijerinckii Fanp3 is an ideal candidate for the fermentative hydrogen production.     

Sequencing batch reactor enhances bacterial hydrolysis of starch promoting continuous bio-hydrogen production from starch feedstock

Bio-hydrogen production from starch was carried out using a two-stage process combining thermophillic starch hydrolysis and dark H₂ fermentation. In the first stage, starch was hydrolyzed by Caldimonas taiwanensis On1 using sequencing batch reactor (SBR). In the second stage, Clostridium butyricum CGS2 was used to produce H₂ from hydrolyzed starch via continuous dark hydrogen fermentation. Starch hydrolysis with C. taiwanensis On1 was operated in SBR under pH 7.0 and 55 °C. With a 90% discharge volume, the reducing sugar (RS) production from SBR reactor reached 13.94 g RS/L, while the reducing sugar production rate and starch hydrolysis rate was 0.92 g RS/h/L and 1.86 g starch/h/L, respectively, which are higher than using other discharge volumes. For continuous H₂ production with the starch hydrolysate, the highest H₂ production rate and yield was 0.52 L/h/L and 13.2 mmol H₂/g total sugar, respectively, under a hydraulic retention time (HRT) of 12 h. The best feeding nitrogen source (NH₄HCO₃) concentration was 2.62 g/L, attaining a good H₂ production efficiency along with a low residual ammonia concentration (0.14 g/L), which would be favorable to follow-up photo H₂ fermentation while using dark fermentation effluents as the substrate.     

The Multifunctional Sactipeptide Ruminococcin C1 Displays Potent Antibacterial Activity In Vivo as Well as Other Beneficial Properties for Human Health

The world is on the verge of a major antibiotic crisis as the emergence of resistant bacteria is increasing, and very few novel molecules have been discovered since the 1960s. In this context, scientists have been exploring alternatives to conventional antibiotics, such as ribosomally synthesized and post-translationally modified peptides (RiPPs). Interestingly, the highly potent in vitro antibacterial activity and safety of ruminococcin C1, a recently discovered RiPP belonging to the sactipeptide subclass, has been demonstrated. The present results show that ruminococcin C1 is efficient at curing infection and at protecting challenged mice from Clostridium perfringens with a lower dose than the conventional antibiotic vancomycin. Moreover, antimicrobial peptide (AMP) is also effective against this pathogen in the complex microbial community of the gut environment, with a selective impact on a few bacterial genera, while maintaining a global homeostasis of the microbiome. In addition, ruminococcin C1 exhibits other biological activities that could be beneficial for human health, as well as other fields of applications. Overall, this study, by using an in vivo infection approach, confirms the antimicrobial clinical potential and highlights the multiple functional properties of ruminococcin C1, thus extending its therapeutic interest.     

Carvacrol and trans-Cinnamaldehyde Reduce Clostridium difficile Toxin Production and Cytotoxicity in Vitro

Clostridium difficile is a nosocomial pathogen that causes a serious toxin-mediated enteric disease in humans. Reducing C. difficile toxin production could significantly minimize its pathogenicity and improve disease outcomes in humans. This study investigated the efficacy of two, food-grade, plant-derived compounds, namely trans-cinnamaldehyde (TC) and carvacrol (CR) in reducing C. difficile toxin production and cytotoxicity in vitro. Three hypervirulent C. difficile isolates were grown with or without the sub-inhibitory concentrations of TC or CR, and the culture supernatant and the bacterial pellet were collected for total toxin quantitation, Vero cell cytotoxicity assay and RT-qPCR analysis of toxin-encoding genes. The effect of CR and TC on a codY mutant and wild type C. difficile was also investigated. Carvacrol and TC substantially reduced C. difficile toxin production and cytotoxicity on Vero cells. The plant compounds also significantly down-regulated toxin production genes. Carvacrol and TC did not inhibit toxin production in the codY mutant of C. difficile, suggesting a potential codY-mediated anti-toxigenic mechanism of the plant compounds. The antitoxigenic concentrations of CR and TC did not inhibit the growth of beneficial gut bacteria. Our results suggest that CR and TC could potentially be used to control C. difficile, and warrant future studies in vivo.     

四川省肉毒梭菌PCR基因分型方法比较研究

目的比较分析4种肉毒毒素(botulinum neurotoxins,Bo NT)基因分型方法,为四川省监测和食物中毒中肉毒梭菌(Clostridium botulinum)分型鉴定提供可靠的方法。方法使用本实验室保存的6株肉毒梭菌(包括A、B、E型)验证4种肉毒梭菌PCR基因分型鉴定方法——美国食品药品监督管理局(FDA)多重PCR分型方法、国际标准化组织(ISO)的两种多重PCR分型方法和一种实时荧光PCR分型方法,比较方法间的差异,并初步分析差异原因。结果 3种多重PCR方法均可在一个反应中同时检测A、B、E 3种型别肉毒梭菌。ISO多重PCR方法 1中A型检测虽能获得预期条带,但结果条带不清晰。其余两种多重PCR方法在分型检测肉毒梭菌时,可获得清晰的预期条带。实时荧光PCR分型方法能在多重反应体系中同时检测到不同型的肉毒梭菌,但由于荧光标记相同,要获得分型结果需要分别检测各毒素型别。结论美国FDA多重PCR方法和ISO多重PCR方法 2操作较简单易行,可在四川省肉毒梭菌监测中推荐使用。     

肠道梭菌在机体能量过度摄入中的作用

肥胖与肠道菌群对能量的过度摄入有密切的关系。目前发现人体肠道中与肥胖有关的细菌主要有厚壁菌门和拟杆菌门细菌,其中梭菌属是厚壁菌门中非常重要而且数量庞大的一类菌。研究表明肠道梭菌属细菌代谢是导致机体能量摄入过度的主要原因之一。此外,肠道菌的多糖水解酶降解膳食纤维产生短链脂肪酸提供机体额外的能量,细菌脂多糖的吸收增多促进机体能量过度摄入,饥饿诱导脂肪因子的表达受到抑制时能量更容易以脂肪的形式蓄积,这些因素均与肥胖的形成有密切关系。但是目前对肠道梭菌在以下几个方面的作用仍未被阐明:1)梭菌是否是多糖水解酶的主要来源;2)多糖水解酶产生的短链脂肪酸对能量摄入的贡献;3)梭菌占优对细菌脂多糖的产生与吸收的影响;以及4)梭菌对FIAF表达的影响等。本文提出了可能的机制,为进一步的研究提供参考。     

Construction of a computer-controlled thermoresistometer for the determination of the heat resistance of bacterial spores over the temperature range 100 to 150°C

A computer-controlled thermoresistometer for the determination of the heat resistance of bacterial spores has been designed and constructed. The thermoresistometer is capable of operating between 100 and 150°C0.1°C with exposusre times as short as 0.1 sec. Five samples (0.01 ml) of spore suspension can be exposed to steam at each time/temperature combination using a computer-controlled piston-driven exposure system. Temperature control of the apparatus is achieved using platinum resistance probes linked to the computer, which then actuates a variable steam control valve.     

THE CLOSTRIDIUM THERMOCELLUM-CLOSTRIDIUM THERMOSACCHAROLYTICUM ETHANOL PRODUCTION PROCESS: NUTRITIONAL STUDIES AND SCALE-DOWN

The Clostridium thermocellum-Clostridium thermosaccharolyticum mixed culture system has been scaled down into flasks in defined medium MJ with Solka Floe as carbon source. The best saccharolytic culture for use with the cellulolytic, anaerobic thermophile C. thermocellum ATCC 27405 was found to be C. thermosaccharolyticum HG-8 when compared to Clostridium thermo-hydrosulfuricum strain 39E or Thermoanaerobacter ethanolicus ATCC 31937. The defined medium was optimized for a high cellulose concentration by increasing the level of FeSO₄ and by replacing 3-[N-morpholino] propane sulfonic acid (MOPS) buffer by sodium bicarbonate.