Production of propionic acid by microbiological way. Part 1. Influence of the initial sugars and product concentrations

The best yields and productivities of 0.38 g · g^?1 and 0.35 g · l^?1 h^?1, respectively, for the propionic acid production in a batchsystem using sugar-cane final molasses as carbon source were obtained when an initial TRS concentration of 50 g · l^?1 was used. It was obvious that this process is severely inhibited by the acids produced and the most drastic effect (μ = 0) was at a TVA concentration near to 250 mmol · l^?1, independently of the initial TRS concentration employed. A generalizated equation of noncompetitive inhibition was adjusted: and kinetic inhibition constants for each initial TRS concentration studied were estimated.     

Influence of different vitamin-nitrogen sources on cell growth and propionic acid production from sucrose by Propionibacterium shermanii

Cell growth and organic acid production by Propionibacteria are dependent on the vitamin-nitrogen source in the culture medium. Final cell and propionic acid concentrations produced by Propionibacterium shermanii, using corn-steep liquor, were higher than those obtained utilizing yeast extracts. Since corn-steep liquor is much cheaper than yeast extract, the process becomes more attractive. By calculating the specific growth rates, it was observed that the critical propionic acid concentration, that prevents all growth (μ_X = 0), is different depending on the vitamin-nitrogen source used and its concentration. For example, for 5.0 and 15.0 g/l Oxoid yeast extract, those critical propionic acid concentrations were 16.0 and 27.0 g/l, respectively. Such propionic acid concentrations inhibit the cell growth, but not the formation of acid. The specific propionic acid production rate also indicates that the critical concentration for metabolic activity, when propionic acid is no longer produced (μ_P = 0), varies according to the vitamin-nitrogen source and its concentration in the medium. For 5.0 and 15.0 g/l Oxoid yeast extract, those concentrations were 22.1 and 30.1 g/l, respectively.     

Production of propionic acid by mixed bacterial fermentation

Summary VariousPropionibacteria andLactobacilli have been grown in starch based media in pure and mixed cultures to ascertain the optimum conditions for propionic acid production. A system has been identified using.Propionibacterium freudenreichii ssshermanii grown in mixed culture withLactobacillus amylophilus that yields approximately 20g/l propionic acid from a medium consisting of wheat flour and corn steep liquor. Simple processing of fermentation broths results in a product containing approximately 30% (w/w) propionic acid that may be suitable for use as a food preservative.     

Batch production of propionic acid by immobilizedPropionibacterium sp

Whole cells ofPropionibacterium freudenreichii subsp.shermanii (two strains) were immobilized in a living state in 2 and 4% alginate gel and 2, 4 and 6% carrageenan gel. Production of propionic acid, acetic acid, and vitamin B₁₂ were examined. The best results were obtained in the fermentation with strains immobilized in 4% alginate gel when applied for the third time.     

Effect of pH on growth and ethanol production byZymomonas

Summary In a mineral salts medium containing yeast extract, NH₄Cl and glucose (50g/L), the pH range producing the fastest growth ofZ. mobilis was 5.5–6.5 with an apparent optimum at 6.5. At constant growth rate of 0.15hr^–1, the specific rates of glucose utilization (q_s) and ethanol production (q_p) were relatively unaffected by pH over the range 7.0–5.5 but increased sharply as the pH was further decreased below 5.5 to 4.0. Under these conditions the ethanol yield was unaffected by pH over the range 4.0–6.5 but decreased markedly at pH of 7.     

Continuous production of Emmental cheese flavours and propionic acid starters by immobilized cells of a propionic acid bacterium

Summary Characteristics of a continuous reactor with Propionibacterium cells entrapped with Ca-alginate are described. For a dilution rate D=0.45 h^–1, the gel produced 8 g.l^–1 for volatile fatty acids and 0.18 g.l^–1 for diacetylacetoin. The fiability of the process and its ability to produce propionic acid bacterium starter at the rate 4.10⁹ cells.l^–1 gel.h^–1 maked it attractive for industrial applications.     

Interactive effects of propionic acid and temperature on growth and ochratoxin a production byPenicillium aurantiogriseum

Propionate at concentrations up to 0.05% decreased at 25 °C the growth and sporulation ofPenicillum aurantiogrseum. The standard size of conidiogeneous structures (metulae, phialids) and conidia was diminished. The effect was more pronounced at a higher temperature (30°C). Inhibition of ochratoxin production by propionate was also demonstrated.     

Production of propionic acid from whey permeate by sequential fermentation, ultrafiltration, and cell recycling

This article deals with the production by fermentation of a mycostatic and aromatic food additive based on propionic acid. Membrane bioreactors have been used from laboratory scale up to pilot and industrial production plants. Due to the high cell densities achieved by the sequential recycling mode of operation, a mixed acids solution was rapidly produced from whey permeate. The sterile fermented broth obtained was subsequently concentrated at different levels by evaporation and spray drying according to the projected use. Concentrated Propionibacterium cells (200 g . L(-1) DW) were obtained from the process by periodic bleeds and could be used to good effect as cheese starters, silage preservatives, or probiotics. Propionic acid concentrations from 30 to 40 g . L(-1) were easily achieved with no residual lactose. The highest volumetric productivity was 1.6 g . L(-1) . h(-1) for total acid and 1.2 g . L(-1) . h(-1) for propionic acid with a specific productivity of 0.035 h(-1). (c) 1993 John Wiley & Sons, Inc.     

Effect of water activity and pH on growth and toxin production by Clostridium botulinum type G.

The combined effect of water activity (aw) and pH on growth and toxin production by Clostridium botulinum type G strain 89 was investigated. The minimum aw at which growth and toxin formation occurred was 0.965, for media in which the pH was adjusted with either sodium chloride or sucrose. The minimum pH (at the optimum aw) for growth and toxin production of C. botulinum type G was found to be 5.6. Optimum conditions for toxin activation were a trypsin concentration of 0.1%, a pH of the medium of 6.5, and an incubation for 45 min at 37 degrees C. These data did not show evidence of heat-labile spores, since a heat shock of 75 degrees C for 10 min did not significantly decrease the spore count of strain 89G in media at pH 7.0 or 5.6. It was frequently observed that cells grown at reduced aw or pH experienced severe morphological changes.     

Effect of pH on growth of acid stream algae

Five species of algae (Chlamydomonas applanata var. acidophila, Euglena mutabilis, Gloeochrysis turfosa, Hormidium rivulare, Stichococcus bacillaris) were isolated from a stream at pH 2·6–3·1, and their laboratory growth studied. Growth of all species could occur at pH values lower than those from which they were isolated, the lowermost limits being quite similar to those recorded for the particular species growing anywhere in England. Morphological differences were apparent with all five species at the lowermost pH values. These took place with Stichococcus bacillaris at pH values at which there was little reduction in growth rate, but with the other species obvious differences in morphology were correlated with a marked reduction in growth rate below the optimum rate. At the uppermost pH value tested, however, no obvious morphological differences were apparent. The effect of including 10% stream water in the medium was rather similar for all five species. No influence on growth rate was detectable at the lower pH values, but higher pH values led to a decrease in growth rate as compared with that found in medium lacking stream water.     

水培条件下pH值对柳枝稷幼苗生长发育的影响

土壤的p H值是限制植物生长发育的一个关键因素。柳枝稷是一种可作为牧草,水土保持的多年生C4能源植物。试验在水培条件下,利用裂区试验设计,以柳枝稷品种(系)为主区,水培液p H值为副区,对反映柳枝稷幼苗生长发育状况的指标进行统计分析。结果显示,随水培液p H值的酸碱强度增大,柳枝稷不同品种(系)幼苗的分蘖数、株高、苗鲜重、根冠比、根系活力以及净光合速率都极显著降低(P0.01),而幼苗保护酶活性以及丙二醛(MDA)含量则极显著升高(P0.01)。尤其是当PH值低于5.0时,幼苗的受到的胁迫更为明显,幼苗超氧化物歧化酶(SOD)和过氧化物酶(POD)活性反而急剧下降。与酸胁迫(p H值7.0)相比,柳枝稷对碱胁迫(p H值7.0)的适应能力更强,其中以西稷2号的抗逆性表现最好。因此应用柳枝稷在边际土壤地区推广种植时,要尽量避免强酸性土壤(p H值5.0),且选用西稷2号品系较为适宜。     

Studies on the amino acid fermentation. Part 1. Production of L-glutamic acid by various microorganisms

Screening tests for glutamate producing strains were carried out, with the media containing carbohydrate and ammonia source as chief ingredients. Glutamate as well as certain other amino acids was detected by paper chromatography in culture broth of many microorganisms tested. Accumulation of L-glutamate in a significant amount (at least a few mg of glutamate per ml of broth) has been demonstrated by various strains of bacteria, streptomycetes, yeasts, and fungi. The highest level of glutamate production has been obtained by a new species of Micrococcus, yielding as much as 0.25 mole of it from one mole of glucose. The courses of fermentations mainly by known strains of microorganisms are shown. The importance of the cultural condition and strain specificity for the production of amino acids are briefly described.     

Effect of pH and acetic acid on growth and 2,3-butanediol production of Enterobacter aerogenes in continuous culture

Summary The effect of pH and acetic acid on growth and 2,3-butanediol production of Enterobacter aerogenes from glucose was investigated in a microaerobic continuous culture. At a dilution rate of 0.20 h^–1 and a fixed oxygen uptake rate (OUR) of 31.5 mmol l^–1 h^–1 the biomass concentration increased with pH ranging from 5.0 to 7.0, while the specific ATP requirement of the cells decreased. In the pH range 5.5–6.5 the product concentration (butanediol + acetoin) was maximal and nearly constant. However, the specific production continuously declined with increasing pH. Experiments with addition of acetic acid showed that the various effects of pH are due to inhibition of the by-product acetic acid on cell growth. The strength of the acetic and inhibition depended only on the concentration of its undissociated form [HAc]. The biomass concentration and the specific OUR were also only functions of [HAc], irrespective of the pH. Although the specific ATP requirement (q ATP) strongly depended on the pH, [HAc] at constant pH. Offprint requests to: W.-D. Deckwer