Effect of fatty acid supplementation on the lipid composition of Mycobacterium smegmatis ATCC 607, grown at 27° and 37°C

Mycobacterium smegmatis ATCC 607 was grown at 27 and 37°C, with and without exogenous unsaturated fatty acids, viz. elaidic, oleic and palmitoleic acids, added to the growth medium. The total lipid content of M. smegmatis ATCC 607 was lower at 27°C, and with added oleic acid, when compared with the controls, but higher in presence of palmitoleic acid. At 37°C no significant differences were noted in the total lipid content. In general, the total lipid content was lower with all of the fatty acid supplementations at both 27 and 37°C. The phosphatidylethanolamine content was slightly higher at 27°C in the presence of elaidic or palmitoleic acid, but was markedly lower with oleic acid supplementation at 37°C. The cardiolipin content was lower in the presence of any of the fatty acids at 27°C, and higher in the medium supplemented with elaidic or oleic acid at 37°C. The unsaturated to saturated fatty acids ratio was higher with palmitoleic acid supplementation at 27°C, but remained unchanged in cells grown at 37°C. The modifications in mycobacterial lipids are a reflection of the organism's ability to adapt to changing growth conditions.     

Influence of acidity and initial substrate temperature on germination of Rhizopus oligosporus sporangiospores during tempe manufacture

J.C. DE REU, F.M. ROMBOUTS AND M.J.R. NOUT. 1995. During the soaking of soya beans according to an accelerated acidification method organic acids were formed, resulting in a pH decrease from 6·0 to 3·9. After 24 h of fermentation at 30°C, lactic acid was the major organic acid (2·1% w/v soak water), while acetic acid (0·3% w/v soak water) and citric acid (0·5% w/v soak water) were also found. During cooking with fresh water (ratio raw beans: water, 1: 6·5) the concentrations of lactate/lactic acid and acetate/acetic acid in the beans were reduced by 45% and 51%, respectively.
The effect of organic acids on the germination of Rhizopus olgosporus sporangiospores was studied in liquid media and on soya beans. Germination in aqueous suspensions was delayed by acetic acid: within 6 h no germination occurred at concentrations higher than 0·05% (w/v incubation medium), at pH 4·0. When soya beans were soaked in the presence of acetic acid, the inhibitory concentration depended on the pH after soaking. Lactic acid and citric acid enhanced germination in liquid medium, but not in tempe.
Inoculation of soya beans with R. oligosporus at various temperatures followed by incubation at 30°C resulted in both increased and decreased periods for the lag phase of fungal growth. A maximum difference of 3 h lag phase was found between initial bean temperatures of 25 and 37°C.
When pure cultures of homofermentative lactic acid bacteria were used in the initial soaking process, less lactic acid and acetic acid was formed during soaking than when the accelerated acidification method was used. This resulted in a reduction of the lag phase before growth of R. oligosporus by up to 4·7 h.     

Factors affecting the survival of Salmonella and Escherichia coli in anaerobically fermented pig waste

The survival of Salmonella typhimurium was investigated in acidogenic, anaerobically fermented pig wastes and in synthetic media, each containing volatile fatty acids (VFA). Salm. typhimurium survived at pH 6·8, but not at pH 4·0, when incubated at 37°C for 24 h in either fermented or synthetic medium containing VFA. The minimum inhibiting concentration of VFA for Salm. typhimurium after 48 h incubation at 30°C at pH 4·0 was 0·03 mol/l and for Escherichia coli it was 0·09 mol/l. Fermented pig wastes in a digester, maintained at pH 5·9, were inoculated with Salm. typhimurium and then incubated at 37°C for 24 h. The pH was adjusted to either 4·0 or 5·0 and after a further 48 h at 30°C, Salm. typhimurium survived at pH 5·0 but not at pH 4·0. It was concluded that pH is critical in determining the survival of this organism in acidogenic anaerobically fermented pig waste.     

Effects of culture conditions on Pectinatus cerevisiiphilus and Pectinatus frisingensis metabolism: a physiological and statistical approach

The genus Pectinatus has been often reported in beer spoilage with off-flavours. The bacteria are strictly anaerobic, Gram-negative rods. Propionate and acetate are the main fermentation products from glucose in the two species belonging to the genus, P. cerevisiiphilus and P. frisingensis. Amino acids routinely present at a high level in beer were not growth substrates for both species, and a significant accumulation of succinate was observed with lactate as growth substrate. Both Pectinatus ssp. showed almost identical fermentation balances on glucose. Growth kinetics of both glucose-grown species were unchanged under a N₂, H₂ or 20% CO₂-containing atmosphere. Combinations of culture medium pH values from pH 3·9 to pH 7·2, of glucose levels between 5 and 55 mmol l^-1, and of lactate concentrations varied from 4 to 40 mmol l^-1 demonstrated that biomass and volatile fatty acids production were proportional to glucose concentration for both Pectinatus species. A significant increase of volatile fatty acid production was measured for both species at the lowest pH values with a lactate or a glucose concentration increase. The maximum biomass production was observed at pH 6·2 for P. cerevisiiphilus , and between pH 4·5 and pH 4·9 for P. frisingensis. Glucose and lactate or pH value were dependent with regard to propionate and acetate production in P. frisingensis. On the other hand, the variations of these three parameters were independent with regard to biomass production for both strains, and to volatile fatty acids production for P. cerevisiiphilus. Addition of ethanol to glucose-grown cultures completely inhibited growth at 1·3 mol l^-1 ethanol for P. cerevisiiphilus , and at 1·8 mol l^-1 for P. frisingensis.     

Production and stability of pediocin N5p in grape juice medium

The production and stability of pediocin N5p from Pediococcus pentosaceus , isolated from wine, were examined in grape juice medium. Maximum growth and higher titre (4000 U ml^-1) were observed at a initial pH of 7·5 and 30°C. The activity of the inhibitory substance was stable between pH values from 2·0 to 5·0 at 4° and 30°C. At pH 10·0 it was completely inactivated. When submitted to 30 min at 80°, 100° and 115°C, maximal stability was observed at pH 2·0. Ethanol up to 10% did not affect pediocin activity at acid pH, nor did 40–80 mg 1^-1 SO₂, independently or combined with different ethanol concentrations, affect inhibitory activity.     

Removal of gaseous n-valeric acid in the air by Rhodococcus sp. B261 immobilized onto ceramic beads

n-Valeric acid, one of the main malodorous pollutants from livestock houses was eliminated with a biofilter prepared with Rhodococcus sp. B261 immobilized onto ceramic beads. The strain was isolated from composted pig faeces and grown in an artificial medium containing volatile fatty acids as a carbon source. The cells were immobilized onto ceramic beads in vacuo. The beads were aseptically incubated at 37 °C, pH 8.0, for 24h for activation of the cells. The beads with immobilized cells (3.36×10⁹ c.f.u./g ceramic beads) and moisture content of 35% (w/w) were packed into a glass column equipped with a water jacket to keep the temperature constant. One hundred-seventy ppm of gaseous n-valeric acid were removed for 11 days at 30h ^-1 (space velocity) and 37 °C.     

Growth of Candida ingens on Supernatant from Anaerobically Fermented Pig Waste: Effects of Temperature and pH

Candida ingens, a pellicle-forming yeast utilizing volatile fatty acids, grew over a pH range of 4.1 to 6.0 on nonsterile supernatants from anaerobically fermented pig wastes; growth was inconsistent between pH 4.1 and 4.6. When ambient temperature above the pellicle was 21°C and the temperature of the medium was 29 to 32°C, a pH range of 4.8 to 5.0 gave yields of 1.90 to 3.31 g of dry matter per liter, and 0.059 to 0.065 mol of volatile fatty acids was utilized per liter. There was no advantage in utilization of volatile fatty acids and yield of dry matter in keeping the pH constant during a 24-h growth period. C. ingens grew at pH 4.8 and 5.0 when both ambient and medium temperatures were 30°C. When ambient temperature was 10°C, maximum yield and utilization of volatile fatty acids occurred at a medium temperature of 28 to 30°C.     

Effect of culture pH on the extracellular production of 5-aminolevulinic acid by Rhodobacter sphaeroides from volatile fatty acids

Summary 5-Aminolevulinic acid(ALA) production by Rhodobacter sphaeroides was investigated at various pH with levulinic acid addition using a volatile fatty acids medium prepared from the mandarin orange peel supplemented with glycine. At neutral pH (6.8 and 7.0), extracellular ALA production was up to 16 mM, while low production of ALA(less than 3.5 mM) was observed at acidic pH (lower than 6.5) and less than 3.9 mM of ALA produced at alkaline pH (higher than 7.5). The higher ALA synthase activity observed at neutral pH might enhance the ALA production compared with that observed in acidic and alkaliphilic cultures.     

Enzymatic properties of lipase and characteristics production byLactobacillus delbrueckii subsp.bulgaricus

Some properties of an extracellular lipase produced byLactobacillus delbrueckii subsp.bulgaricus were studied. Maximum enzyme activity was found against olive and butter oil as enzyme substrates. Addition of 9% acacia gum, 0.1% Na-deoxycholate and 0.01 M CaCl₂ to the enzyme reaction mixture increased-lipase activity from 5.3 to 14.5 (FFA/mg protein/minute) at pH 6.0 and at 40° C. Maximum lipase production was reached in the presence of glucose as a sole source of carbon, wheat bran as nitrogen source, olive oil as a sole lipid source and butyric acid as fatty acid supporting the growth medium. An initial pH value of the culture medium of 6.0 and a temperature of 35° C gave the highest lipolytic activity.     

Cell location and partial characterization of Brochothrix thermosphacta and Lactobacillus curvatus lipases

The lipases of Brochothrix thermosphacta and Lactobacillus curvatus were in the soluble fraction of the cell and not membrane- or wall-bound. Their optimal activities were around pH 6mD5 and at 37°C. Enzymes were stable between 4 and 30°C and at freezing temperatures (— 20°C and —60°C). The lipase of Lact. curvatus was stable in the pH range of 4mD0 to 11mD0, whereas that of B. thermosphacta was denatured at pH lower than 5mD0 and greater than 9mD0. Among triglycerides tested, maximal activity was found with tributyrin and hydrolysis of other triglycerides decreased as the length of fatty acid increased.     

Amylolytic lactic acid bacteria in fish silage

An ∝aL-amylase activity has been observed in lactic acid bacteria occurring initially in fermented fish silage. The organisms belong to the genus Leuconostoc . The main fraction of the amylolytic enzyme produced by one of the isolated bacteria is cell-bound and is released into the medium at a late stage of growth. Treating cells with ultrasound or Triton X-100 increases enzyme activity in the culture filtrate. The pH range for enzyme activity is 5.0–7.0, with an optimum at pH 6.0. The enzyme is extremely labile at pH 8.0 and is inactivated at temperatures above 50°C at pH 5.8. Two enzyme fractions were found by isoelectric focusing, the main one at pH 5.00 and another at pH 4.5. Chromatography on DEAE cellulose gave two active peaks.     

Effect of ethanol on the palmitate-induced uncoupling of oxidative phosphorylation in liver mitochondria

The effect of ethanol on the uncoupling activity of palmitate and recoupling activities of carboxyatractylate and glutamate was studied in liver mitochondria at various Mg²⁺ concentrations and medium pH values (7.0, 7.4, and 7.8). Ethanol taken at concentration of 0.25 M had no effect on the uncoupling activity of palmitic acid in the presence of 2 mM MgCl₂ and decreased the recoupling effects of carboxyatractylate and glutamate added to mitochondria either just before or after the fatty acid. However, ethanol did not modify the overall recoupling effect of carboxyatractylate and glutamate taken in combination. The effect of ethanol decreased as medium pH was decreased to 7.0. Elevated concentration of Mg²⁺ (up to 8 mM) inhibits the uncoupling effect of palmitate. Ethanol eliminates substantially the recoupling effect of Mg²⁺ under these conditions, but does not influence the recoupling effects of carboxyatractylate and glutamate. It is inferred that ADP/ATP and aspartate/glutamate antiporters are involved in uncoupling function as single uncoupling complex with the common fatty acid pool. Fatty acid molecules gain the ability to migrate under the action of ethanol: from ADP/ATP antiporter to aspartate/glutamate antiporter on addition of carboxyatractylate and in opposite direction on addition of glutamate. Possible mechanisms of fatty acid translocation from one transporter to another are discussed.     

Ex situ volatile survey of ground almond and pistachio hulls for emission of spiroketals: Analysis of hull fatty acid composition,water content,and water activity

The spiroketal conophthorin has recently been implicated as an important semiochemical of the navel orangeworm moth (Amyelois transitella), a major insect pest to California tree nuts. Additionally, new evidence demonstrates that fungal spores in the presence of linoleic acid produce conophthorin. Numerous investigations have analyzed the volatile emissions of almonds and pistachios under varying conditions, yet there are few reports of conophthorin as a volatile component. Previous studies by our laboratories have suggested almond hulls may be a source of conophthorin production. Accordingly, the volatile emissions of ex situ almond and pistachio ground hulls were surveyed at several developmental stages. Each ground sample was analyzed at various intervals to determine if conophthorin was produced. The almond and pistachio samples were presumed to have a natural fungal bouquet present. Additionally, the fatty acid composition, water content, and water activity of the hulls were analyzed for each sample. Conophthorin and the structurally similar compound chalcogran were detected from almond hulls and shells, but not from the pistachio samples. The almond and pistachio hulls were investigated for four fatty acid components – palmitic, oleic, linoleic, and linolenic. The fatty acid composition of almond hulls varied greatly throughout the growing season, whereas the composition of pistachio hulls remained relatively constant. Both water content and activity were constant in early stages of almond growth then dropped in the later stages of hull split. Spiroketal emission along with other associated volatiles is discussed. This is the first report of the fatty acid composition, water content, and water activity of developing almond and pistachio hulls.     

Enzymatic synthesis of l-ascorbyl linoleate in organic media

A novel l-ascorbyl fatty acid ester, l-ascorbyl linoleate was successfully prepared by enzymatic esterification and transesterification in a non-aqueous medium using immobilized lipase as biocatalyst. Changes in enzymatic activity and product yield were studied for the following variable: the nature of the fatty acid, the fatty acid concentration and water content. The yield of synthesis for the C18 unsaturated fatty acids were higher than for the C18 saturated fatty acid. Initial enzyme concentration does not affect the equilibrium of the reaction. And the product yield (33.5%) in the transesterification was higher than that of the esterification (21.8%) at a high-substrate concentration 0.3 M. The medium water content was found to have a distinct influence on the l-ascorbyl linoleate synthesis.These authors contributed equally to the article.     

The combined effect of incubation temperature, pH and sorbic acid on the probability of growth of non-proteolytic, type B Clostridium botulinum

L und , B.M., G raham , A.F., G eorge , S.M. & B rown , D. 1990. The combined effect of incubation temperature, pH and sorbic acid on the probability of growth of non-proteolytic, type B Clostridium botulinum. Journal of Applied Bacteriology 69 , 481–492.
It has been reported that non-proteolytic strains of Clostridium botulinum will grow at 3.3°C, and they are therefore of concern in relation to certain chilled foods. The effects of combinations of inhibitory factors may be used to reduce the risk of growth of these bacteria in foods. The combined effect of pH values between 4.8 and 7.0, temperatures between 6° and 30°C, and sorbic acid concentrations up to 2270 mg/1 on the probability of growth from a single spore of non-proteolytic, type B strains in a culture medium has been determined. A mathematical model has been developed that enables the effect of varying combinations of these factors on the probability of growth of non-proteolytic, type B Cl. botulinum to be predicted.     

Influence of particle size and pH on anaerobic degradation of cellulose by ruminal microbes

Batch experiments were performed to investigate the influence of cellulose particle size and pH on the anaerobic degradation of crystalline cellulose by ruminal microbes. At a particle size of 50 μm there was a higher hydrolysis and acidogenesis rate, and a reduced degradation time, than for 100-μm particles. Reduction in cellulose particle size resulted in decreased methane production, but an increase of soluble products. Cellulose degradation increased with pH from pH 6.0 to 7.5, whereas at pH⩽5.5 there was no degradation. The inhibitory effect of low pH (⩽5.5) on ruminal microbes was not completely remedied even when the pH of the medium was adjusted to a neutral range. In an anaerobic cellulosic waste degrading system inoculated with ruminal microbes the fermentation system should therefore be maintained above pH 6.0. In all cases, volatile fatty acids were the major water-soluble products of cellulose degradation; acetate and propionate accounted for more than 90% of the volatile fatty acid total.     

S-Adenosylmethionine,cyclopropane fatty acid synthase,and the production of lactobacillic acid in Lactobacillus plantarum

S-Adenosylmethionine (AdoMet) levels in Lactobacillus plantarum were found to increase concomitantly with the production of membrane cyclopropane fatty acids under normal growth conditions. This increase in AdoMet did not occur when the pH of the culture medium (initially pH 6.5) was not allowed to fall (pH 4 or lower) during growth. When the culture medium was maintained at pH 6.5, cyclopropane fatty acid synthesis also remained low. While the activity of cyclopropane fatty acid synthase is increased as the pH decreases, the activity of AdoMet synthetase is largely unaffected by the variation of pH of the culture medium. The production of cyclopropane fatty acids is also dependent upon continued protein synthesis; in the presence of chloramphenicol cyclopropane fatty acid synthase activity is decreased, resulting in a lowered production of cyclopropane fatty acids. A dramatic increase in AdoMet levels occurs in the presence of chloramphenicol. It is proposed that AdoMet levels, in conjunction with cyclopropane fatty acid synthase activities, regulate cyclopropane fatty acid synthesis in L. plantarum.     

Mercury inhibition of avian fatty acid synthetase complex.

(1) Subcutaneous or intra-abdominal injections of 8 mg of HgCl2/100 g body weight markedly depressed hepatic fatty acid synthetase activity of chicks at 1 h post-injection. The depression occurred despite the fact that the chicks continued to eat up until the time they were killed. Under these same conditions, the hepatic activity of acetyl-CoA carboxylase (EC 6.4.1.2) was not affected by HgCl2, while the activity of the mitochondrial system of fatty acid elongation was stimulated. (2) When 2-mercaptoethanol was included in the incubation medium for a highly purified preparation of fatty acid synthetase, 500 muM HgCl2 was required to show definite inhibition of the enzyme. When 2-mercaptoethanol was omitted, 50 muM HgCl2 was inhibitory and 100 muM HgCl2 abolished enzyme activity. (3) 2 mM dithiothreitol completely protected the purified fatty acid synthetase preparation from inhibition by 100 muM HgCl2. When dithiothreitol was added after the addition of enzyme to the mercury-containing medium, protection of the enzyme was not complete. (4) Dialysis of cytosol fractions from chicks injected with HgCl2 against 500 vol. of 0.2 M potassium phosphate buffer (pH 7.0) containing 1 mM EDTA and 10 mM dithiothreitol for 4 h at 4 degrees stimulated the fatty acid synthetase activity of the fractions. Dialysis of cytosol fractions from noninjected chicks under the same conditions was without effect on fatty acid synthetase activity. (5) These data support the hypothesis that the inhibitory effect of HgCl2 administered in vivo on hepatic fatty acid synthetase activity in chicks is mediated through the interaction of mercury with the sulfhydryl groups of the enzyme.     

Studies on the Mechanism of the Sporicidal Action of Glutaraldehyde

S ummary . Low concentrations (0.025–0.125%) of glutaraldehyde inhibited or prevented colony formation by Escherichia coli, Bacillus subtilis and B. pumilis in agar, and inhibited germination of spores of the Bacillus spp. in L-alanine plus D-glucose. Higher concentrations (2%) of glutaraldehyde at pH 8.5 were sporicidal. Pre-treatment of spores with glutaraldehyde lessened release of dipicolinic acid when the spores were subsequently heated at 100°, but not at 121°. Spores treated with glutaraldehyde and then with 0.5 M thioglycollic acid in 6 M urea at 70° were less sensitive to lysis by hydrogen peroxide than spores which had not been exposed to glutaraldehyde. Glutaraldehyde was less effective in preventing peroxide induced lysis if added to spores which had been previously exposed to thioglycollic acid plus urea at 70°. The mechanism of the sporicidal activity of glutaraldehyde is discussed in relation to these findings.     

Improvement of 5-aminolevulinic acid production by Rubrivivax benzoatilyticus PS-5 with self-flocculation by co-fermentation of precursors and volatile fatty acids under pH-controlled conditions

Photosynthetic bacteria are known to utilize volatile fatty acids as a carbon source for growth and product formation. In this study, a new isolate, Rubrivivax benzoatilyticus PS-5, possessing self-flocculation properties, was cultivated in modified glutamate-malate (GM) medium containing glutamate and malate as carbon sources. The effect of acetic acid, propionic acid and butyric acid (at 1–4 g L^?1) as co-substrates and 7.5 mM glycine, 10 mM succinic acid as precursors for 5-aminolevulinic acid (ALA) production from R. benzoatilyticus PS-5 was investigated. Among the volatile fatty acids tested, acetic acid was preferred to butyric acid and propionic acid, with the optimum concentrations of 3 g L^?1, 1 g L^?1 and 3 g L^?1, respectively. The highest ALA production was 169.71 μM, 162.16 μM and 46.18 μM, respectively, while the highest productivity was 2.57 μM h^?1, 2.25 μM h^?1 and 0.96 μM h^?1, respectively. The precursor was consumed completely (100 %) while the assimilation of the acetic acid and butyric acid was 62.50 % and 48.65 %, respectively. Supplementation of propionic acid (at 1–4 g l^?1) had a negative effect on growth and ALA production. To increase production efficiency, the pH-control strategy (at pH 6.0–8.0) during fermentation was tested. The optimum pH was 7.0, giving the maximum ALA production of 286.18 μM and a productivity of 3.97 μM h^?1. These values were 1.68-fold and 1.54-fold higher, respectively, than those under uncontrolled pH conditions.