Preparation of extracts of culture liquids for gas-chromatographic determination of non-acidic fermentation products

A simplified extraction method of high efficiency has been worked out to permit the determination of small amounts of alcohols present in fermentation solutions. Methods of extracting are described for large and small amounts of culture media. The proposed method has been successfully applied to known amounts of alcohol in bacterial fermentation solutions. Clostridium acetobutylicum andZymomonas mobilis were used for this investigation. The method is described in details with theClostridium culture.     

Preparation of extracts of culture liquids for gas-chromatographic determination of acidic fermentation products

An extraction method coupled with gas-chromatographic analysis has been devised for the determination of small amounts of C₁-C₇ branched and straight-chain saturated fatty acids as well as 18 mono-, di- and tricarboxylic acids and related compounds, the latter being analyzed either as their methylesters or as their trimethylsilyl-derivatives. Methods for extracting non-volatile acids or both volatile and non-volatile acids are described for large and small volumes of culture media. The proposed methods have been successfully applied to the determination of non-acidic fermentation products, known amounts of alcohols, and to volatile and non-volatile acids in bacterial fermentation solutions, namely a batch culture ofLactobacillus casei subsp.rhamnosus ATCC 7469. A carbon balance sheet of this organism's metabolic behaviour throughout growth is proposed.     

Desmin and Vimentin Intermediate Filament Networks: Their Viscoelastic Properties Investigated by Mechanical Rheometry

We have investigated the viscoelastic properties of the cytoplasmic intermediate filament (IF) proteins desmin and vimentin. Mechanical measurements were supported by time-dependent electron microscopy studies of the assembly process under similar conditions. Network formation starts within 2 min, but it takes more than 30 min until equilibrium mechanical network strength is reached. Filament bundling is more pronounced for desmin than for vimentin. Desmin filaments (persistence length l_p ≈ 900 nm) are stiffer than vimentin filaments (l_p ≈ 400 nm), but both IFs are much more flexible than microfilaments. The concentration dependence of the plateau modulus G₀ ∼ c^α is much weaker than predicted theoretically for networks of semiflexible filaments. This is more pronounced for vimentin (α = 0.47) than for desmin (α = 0.70). Both networks exhibit strain stiffening at large shear deformations. At the transition from linear to nonlinear viscoelastic response, only desmin shows characteristics of nonaffine network deformation. Strain stiffening and the maximum modulus occur at strain amplitudes about an order of magnitude larger than those for microfilaments. This is probably attributable to axial slippage within the tetramer building blocks of the IFs. Network deformation beyond a critical strain γ_max results in irreversible damage. Strain stiffening sets in at lower concentrations, is more pronounced, and is less sensitive to ionic strength for desmin than for vimentin. Hence, desmin exhibits strain stiffening even at low-salt concentrations, which is not observed for vimentin, and we conclude that the strength of electrostatic repulsion compared to the strength of attractive interactions forming the network junctions is significantly weaker for desmin than for vimentin filaments. These findings indicate that both IFs exhibit distinct mechanical properties that are adapted to their respective cellular surroundings [i.e., myocytes (desmin) and fibroblasts (vimentin)].     

Sauerkraut fermentation : New fermentation vat

Summary A new sauerkraut fermentation vat with external recycling of brine is described. This system allows the control of fermentation, improves the homogeneity of final product and accelerates theacidification by the usual lactic-acid bacteria.     

Kocho fermentation

Kocho, an acidic starchy food, is prepared by fermenting a mixture of the scraping of the trunk and pulverized stem and corm of ensette ( Ensette ventricosum). Leuconostoc mesenteroides is responsible for initiating the fermentation. Because of the activities of this species and, to some extent, of Streptococcus faecalis , the pH of the fermenting kocho was reduced from 6˙5 to 5˙6. These organisms were then succeeded by the homofermentative bacteria Lactobacillus coryneformis subsp. coryne-formis and Lact. plantarum . Through the activities of the Lactobacillus species, the pH was further reduced to 4˙2. Pediococcus cerevisiae , although present in kocho, did not achieve prominence because of the relatively low fermentation temperature (14°-18°C). Spore-formers were present in fairly high numbers during the first 15 d of fermentation. It was suspected that the butyrous odour which was detected during the first 2 weeks in fermenting kocho might be due to the activities of certain clostridial species. Yeasts were also present in fairly high numbers.     

Oxygen transfer in liquids

In the laboratory-type airlift tower reactor oxygen transfer from air in tap water and/or polyacrylamide solutions (Neuperm WF) was studied. In order to characterize the system, volumetric coefficient of oxygen transfer was determined by the gassing-out method. Two arrangements of the airlift tower reactor were compared, namely the reactor with and without motionless mixer. In addition, mean relative gas holdup and gas power output were determined for both arrangements.     

发酵抑制物对絮凝酵母戊糖发酵的影响

将絮凝剂加入酵母溶液中,使酵母絮凝成颗粒以此作为固定化酵母进行戊糖发酵。研究了常见发酵抑制物(甲酸、乙酸、糠醛和乳酸等)对絮凝酵母发酵木糖的影响。结果表明:在60.0g/L木糖发酵液中,经过24h发酵,木糖利用率达94.6%,当分别添加抑制物甲酸、乙酸、糠醛、乙醇和乳酸时,聚氧乙烯絮凝酵母分别对其的耐受浓度为0.5、0.5、1.0、30.0和8.0g/L。当抑制物添加量超过各自的耐受浓度后,对絮凝酵母发酵会产生明显的抑制作用。     

Sugaring-out extraction of acetoin from fermentation broth by coupling with fermentation

Bioprocess and Biosystems Engineering - Acetoin is a natural flavor and an important bio-based chemical which could be separated from fermentation broth by solvent extraction, salting-out...     

Optimization of compactin fermentation

A compactin producer Penicillium sp strain was isolated from soil in our screening program. The compactin-biosynthesising capacity of the strain was improved from 5 μg ml⁻¹ to 250 μg ml⁻¹ by mutation-selection method. We investigated the effect of the medium composition on compactin productivity. A central, orthogonal three-factor experimental design by Box and Wilson was used in the investigation. The results were analysed by non-linear regression analysis. The composition of the production medium was optimized according to the calculated mathematical model using the steepest ascent method. The compactin productivity was increased to 400 μg ml⁻¹ by applying this method. Received 08 October 1997/ Accepted in revised form 04 December 1997     

Solid-state fermentation of sugar-beet

Summary Semi solid culture is adaptated to ethanol production from sugar-beet. This technique offers some advantages (reduction of liquid volumes and suppression of the diffusion step). With a tubular reactor, the ethanol concentration obtained reaches 8,3%, and the yield is 0,407. The feasability of solid state fermentation on sugar-beet is demonstrated.     

Bacillus fermentation of soybeans

Kinema fermentations of Indian and Canadian No. 1 soybeans by Bacillus sp. DK-W1 and by mixed cultures of Bacillus sp. DK-W1 and Enterococcus faecium DK-C1 were essentially identical. The viable cell count of Bacillus increased from an initial 10⁵ to 10¹⁰ c.f.u./g wet wt after 48 h incubation at 37°C. The pH of the fermentation dropped from an initial 6.9 to about 6.4 after 8 h and then rose to 8.6 after 32 h, with a coincident increase in proteolytic activity and ammonia concentration. The fermentations containing E. faecium and Bacillus exhibited a greater initial pH decline and a slightly retarded subseqent increase in pH compared with fermentations with Bacillus only. The presence of E. faecium had no detectable effects on growth of the Bacillus, proteolytic activity, ammonia production or the final pH of the fermentations.P.K. Sarkar was and P.E. Cook and J.D. Owens are with the Food Microbial Interactions Laboratory, Department of Food Science and Technology, University of Reading, Reading RG6 2AP, UK; P.K. Sarkar is now with the Microbiology Laboratory, Centre for Life Sciences, University of North Bengal, Siliguri 734430, India.