P. Stevens

Effect of various external factors on the fermentative production of hydrogen gas from glucose by Clostridium butyricum strains in batch culture

Summary The fermentation of glucose by Clostridium butyricum strains NCTC 7423, IFO 3315t1, 3847, 3858 and IAM 19001 was investigated in batch cultures at the defined pH values of 5.5, 6, 7, 7.5 or 8. Acetate, butyrate, lactate, formate, CO 2 and H 2 formations were determined quantitatively. The pH range for growth and fermentation is strain-linked and varies between 5.5–6 (for strain IFO 3847) and 5.5–8 (for strain NCTC 7423). The higher the pH of the fermentation medium, the more the H2 production differs from the one, theoretically expected according to the acetate and butyrate production. For at least one strain (NCTC 7423) formate then serves as an additional electron sink. With increasing incubation pH the acetate/butyrate ratio increases above 1 for strains NCTC 7423, IFO 3315t1, 3858 and IAM 19001. No change in the fermentation pattern occurred with increasing acetate or butyrate concentrations up to 200 mM, except for the maximum velocity of gas production, which slowed down gradually with added butyrate. Between 400 and 500 mM acetate or butyrate added the glucose consumption was completely or almost completely inhibited.

Hydrogen gas production from formate and glucose by different members of the Enterobacteriaceae

SummaryEighteen strains belonging to the Enterobacteriaceae were tested for quantitative H2 gas production from formate and glucose under anaerobic conditions. Within 48 h the converted formate was decomposed into H2 with an efficiency of 90% or more for most of the strains. The conversion efficiencies for glucose into H2 were very much lower: between 4.3 and 8.7%. A specially designed fermentation vessel was used.

An alternative real-time PCR method to detect the Bacillus cereus group in naturally contaminated food gelatine: a comparison study

Aims:  Comparison of an internally controlled real‐time PCR assay with the standard plate‐based assay (ISO 21871) for the detection of Bacillus cereus group cells in gelatine.

Comparative study on H2 evolution from DL-lactate, acetate and butyrate by different strains of Rhodopseudomonas capsulata in a new type of reactor

SummaryNine strains of Rhodopseudomonas capsulata were tested for anaerobic light-dependent H2 production from three different H-donors: DL-lactate, acetate and butyrate. The average H2 conversion efficiency for the three H-donors was respectively: 55.5%, 52.5% and 30.5%. For most strains only minor differences in H2 evolution rate and H2 conversion efficiency were observed.

The effect of temperature and light intensity on hydrogen gas production by different Rhodopseudomonas capsulata strains

SummarySix strains of Rhodopseudomonas capsulata were tested for their ability for anaerobic light-dependent hydrogen gas production from acetate in different incubation temperatures and light intensities.Certain strains show a higher efficiency of acetate conversion to H2 at higher temperatures and higher light intensities, others on the other hand are insensitive or even show the opposite effect.

Relation between pH, Hydrogenase and Nitrogenase Activity, NH+4 Concentration and Hydrogen Production in Cultures of Rhodobacter Sulfidophilus

SUMMARY: Rhodobacter sulfidophilus, a sulphide-tolerant, salt-tolerant member of the Rhodospirillaceae, was shown to produce molecular hydrogen on a mineral medium with lactate as electron donor and glutamate as nitrogen source. A maximum production of about 1·1 mmol H2 (mmol added lactate)−1 was found at pH 6·75. The in vivo activity of hydrogenase and nitrogenase showed that hydrogenase activity (and thus the H2 recycling system) was greatest at pH 6·5 and 6·75 and thus, at least partially, was responsible for the lack of H2 production below 6·75, but that nitrogenase activity was greatest at between pH 6·5 and 7·0, and decreased to zero at pH 8·0, resulting in reduced H2 production at pH 7·5 and none at pH 8·0. When sufficient NH+ 4 had accumulated in the culture, nitrogenase activity remained below the maximum value and no H2 production occurred.

Photoproduction of Molecular Hydrogen by Rhodobacter sulfidophilus

Summary Light-dependent anaerobic hydrogen production by the marine photosynthetic organism Rhodobacter sulfidophilus was investigated and demonstrated with DL-malate, DL-lactate, acetate or butyrate as H-donor. The H 2 production was optimal when the pH of the medium was stabilized at 6.5-6.9 either by increasing the phosphate buffer concentration up to 80 mM or by continuous pH monitoring and correction.

The effect of the H2 partial pressure on the metabolite pattern ofLactobacillus casei, Escherichia coli andClostridium butyricum

SummaryThe metabolite pattern of batch cultures ofLactobacilluscasei LMG 6400,Clostridiumbutyricum LMG 1213t1 andEscherichiacoli LMG 2093 was effected only for the latter organism when the H2 partial pressure was below 1 atmosphere: high hydrogen partial pressures increased the formate formation, low pressures gave rise to increased acetate production and higher cell yields.

An alternative real‐time PCR method for the detection of thermotolerant Bacillus sensu lato contaminants in naturally‐contaminated gelatine

Aims: Comparison of an internally‐controlled real‐time PCR assay with the current plate‐based assay for the detection of Bacillus sensu lato contaminants in gelatine.