Contribution to the study of resistance to drying of lactic acid bacteria (lyophilization)

Ibourahema COULIBALY (2010). Contribution à l’étude de la résistance au séchage des bactéries lactiques (thèse de doctorat en français) ; Université de Liège, Gembloux Agro-Bio Tech, (Belgique), 260 p., 22 tableaux, 39 figures.RésuméL’utilisation de souches lactiques, à l’échelle industrielle, nécessite une sélection sur base des propriétés technologiques, physiologiques et biochimiques, ainsi que la mise enoeuvre de procédés biotechnologiques bien maîtrisés pour leur production et leur conservation. A cet effet, le séchage est une étape importante. Sous forme sèche, le produit est plus facilement manipulable. Cependant au cours du séchage, les microorganismessubissent un stress thermique et/ou osmotique qui se traduit par une perte de viabilité pendant le stockage. L’utilisation d’agents protecteurs au cours du stockage a permis d’obtenir une bonne viabilité. En effet, les bactéries sont soumises pendant la lyophilisation et au cours du stockage à une mortalité liée en grande partie à l’oxydation des acides gras membranaires. L’analyse de ces acides au cours des différents procédés defabrication et de stockage permet de noter la présence des hydroperoxydes. Cette oxydation est engendrée par l’action de l’oxygène sur les acides gras polyinsaturés principalement l’acide linoléique (C18:2) et linolénique (C18:3) ce qui engendre la formation des hydroperoxydes : acide hydroperoxyoctadecadienoique (HPOD) et acide hydroperoxyoctadecatrienoique(HPOT) méthylés ou non en position 13- et 9-. Une analyse des composés secondaires émanant des poudres de bactéries lactiques indique la présence de composés volatils. Parmi ceux-ci, apparaissent des molécules volatiles (principalement des aldéhydes), qui modifient la flaveur d’origine des corps gras. Les études menées au niveau des constituants phospholipidiques de la membrane montrent un lien entre le degré d’oxydation et la mortalité cellulaire au cours du stockage. Les différents phospholipides déterminés au nombre de sept (7) subissent tous cette oxydation à des degrés divers.L’utilisation d’antioxydant au cours du stockage permet d’inhiber les phénomènes de peroxydation des lipides et permet également de maintenir la valeur nutritionnelle (teneur en AGPI, réduction des dérivés peroxydés nocifs) du produit.Ibourahema COULIBALY (2010). Contribution to the study of resistance of lactic acid bacteria subject to drying. (Dissertation in French) ; University of Liège, Gembloux Agro-Bio Tech , (Belgium), p. 260 p., 22 tables, 39 figures.SummaryThe use of lactic strains in industrial scale requires selection on the basis oftechnological, physiological and biochemical properties, as the implementation of biotechnological processes under control for their production and conservation. At this effect drying process is an important step. In dry form, the product is more easily manipulated. However during the drying process, microorganisms undergo heat stress and/or osmotic resulting in a loss of viability during storage. The use of protective agents during storage has resulted in a good viability. In fact, the bacteria are subjected during lyophilization and during storage to a mortality largely oxidation the membrane fatty acids. The analysis of these acids during the process helps to note the presence of hydroperoxydes which are the cause of this mortality. This oxidation is caused by the action of oxygen on polyunsaturated acids linoleic acid (C18:2) and linolenic (C18:3) mostly, causing the formation of hydroperoxydes: hydroperoxyoctadecadienoic acid (HPOD) and hydroperoxyoctadeca-trienoic acid (HPOT) at position 13 - and 9 - methyl or not. An analysis of secondary compounds from the powders indicates the presence of birds.These products appear volatile compounds (mainly aldehydes), hydrocarbons, alcohols, acids etc., which altered the original flavour of fat. Studies in phospholipids constituents of the membrane show a link between the degree of oxidation and cell death during storage. The various phospholipids determined, seven (7) are all undergo this oxidation to various degrees. The use of antioxidants during storage can inhibit the process of lipid peroxydation and helps also to maintain the nutritional value (PUFA content, reduction of harmful peroxide-derived) product

The Resistance to Freeze-Drying and to Storage Was Determined as the Cellular Ability to Recover Its Survival Rate and Acidification Activity

The protective effects of the fatty acid composition and membrane action of the acidification activity of two strains of Lactobacillus kept at 20°C were studied. The addition of sorbitol, monosodium glutamate and glycerol during storage is causing the decline of acidification and increased concentrations of unsaturated fatty acids observed in both strains. The addition of sorbitol and monosodium glutamate does not alter the fatty acid composition, whatever the strain, but increases the resistance to freeze-drying of L. plantarum CWBI-B1419 and improves survival during storage. The addition of these preservatives and decreased activity of acidification improves the ratio unsaturated. These results indicate that the survival during storage and freeze-drying resistance are closely related to the composition of membrane fatty acids. This behaviour can be interpreted as an adaptation of L. plantarum B1419-CWBI supplemented by cryoprotectant additives such as sorbitol or monosodium glutamate sorbitol and monosodium glutamate as an additive. L. plantarum CWBI-B1419 presents a greater adaptation to culture conditions than L. paracasei ssp. paracasei LMG9192T

Evaluation de la qualité marchande, biochimique et organoleptiques des fèves de cacao (Theobroma Cacao L.1753) issues des nouveaux supports de fermentation à soubre dans les régions du De La Nawa (Côte d’Ivoire)

La fermentation des fèves de cacao est une étape très cruciale dans l’obtention des fèves de bonne qualité marchande et organoleptique, des produits dérivés obéissant aux exigences internationales

Characterization of lactic acid bacteria isolated from poultry farms in Senegal

peer reviewedThe group that includes the lactic acid bacteria is one of the most diverse groups of bacteria known and these organisms have been characterized extensively by using different techniques. In this study, thirty lactic acid bacterial strains were isolated from soils chicken faeces and feathers. A total of nineteen isolates were obtained and by sequential screening for catalase activity and Gram-staining, eight were determined to be LAB out of which six were established to be homofermentative by the gel plug test. Five isolates were identified by use of the API 50CHL kit and four Lactobacilli strains and one Lactococci strain were selected to study their growth and lactic acid production profiles in a time course experiment. The Lactobacilli strains, both isolated from faeces, produced higher amounts of cells and lactic acid from soils as compared to the lactococci strain isolated from feathers. L (+)-lactic acid is the only optical isomer for use in pharmaceutical and food industries because is only adapted to assimilate this form. The optical isomers of lactic acid were examined by L (+) and D (-) lactate dehydrogenase kit. Lactobacilli strains produced combination of both optical isomers of lactic acid. Among them, Lactobacillus casei subsp. casei produced the low amount of D (-)-lactic (2%). The optimum rates of glucose for lactic acid production by Lactobacillus strains were 180 and 120 g/l for Lactobacillus plantarum and Lactobacillus paraplantarum, respectively

Influence of Freeze-Dried Yeast Starter Cultures on Volatile Compounds of Tchapalo, a Traditional Sorghum Beer from Côte d’Ivoire

The production of the Ivorian sorghum beer known as tchapalo remains more or less an empirical process. The use of starter cultures was therefore suggested as the appropriate approach to alleviate the problems of variations in organoleptic quality and microbiological stability. In this study, we evaluated the capacity of S. cerevisiae and C. tropicalis to produce sorghum beer as freeze-dried starter in mixed or pure cultures. Beers produced with mixed freeze-dried cultures of S. cerevisiae F12-7 and C. tropicalis C0-7 showed residual sugars and ethanol contents similar to beers obtained with S. cerevisiae F12-7 pure culture, but the total sum of organic acids analyzed was the highest with the mixed culture (15.71 g/L). Higher alcohols were quantitatively the largest group of volatile compounds detected in beers. Among these compounds, 2-phenyl ethanol, a higher alcohol that plays an important role in beer flavor, was highly produced with the mixed culture (10,174.8 µg/L) than with the pure culture (8749.9 µg/L)

Ethanol effect on yeast strains isolated from tchapalo, a traditional sorghum beer from Côte d'Ivoire

The general trend in sorghum beer production is now the use of starter culture to alleviate the problems of variations in organoleptic quality and microbiological stability. In this study, we aimed to select strains of Saccharomyces cerevisiae and Candida tropicalis to use as starter culture based on their ability to face ethanol toxicity. All the strains exhibited a relatively high resistance up to 5% ethanol. At 7.5% ethanol, S. cerevisiae F12-7 and C. tropicalis C0-7 were the most resistant strains with viability rate of 80-97% after 24 h of incubation. These two strains showed also the highest unsaturated/saturated fatty acids ratios. Values increased from 68.86% to 80.30% and from 72.97 to 85.96% respectively for S. cerevisiae F12-7 and C. tropicalis C0-7 cultivated under 0% and 7.5% ethanol. The cellular neutral lipid composition differed markedly according to the yeast strains. With proportion of 36.73% for S. cerevisiae F12-7 and 78.75% for C. tropicalis C0-7, ergosterol was the most abundant neutral lipid founded in the strains membranes. In addition, phosphatidylethanolamine contents decreased with the increase of ethanol concentration in the culture medium on contrary to phosphatidylcholine contents. These two strains were so suggested as starter cultures for sorghum beer production. © All Rights Reserved

Impact of polyunsaturated fatty acid degradation on survival and acidification activity of freeze-dried Weissella paramesenteroides LC11 during storage

Abstract The impact of polyunsaturated fatty acid (PUFA) degradation on the survival and acidification activity of freeze-dried Weissella paramesenteroides LC11 was investigated over 90-days storage at 4 °C or 20 °C in vacuumsealed aluminium foil or glass tubes with two water activities (aw=0.11 or 0.23). Colony counts, acidification activity (% lactic acid/g), linoleic/palmitic (18:2/16:0) or linolenic/palmitic (18:3/16:0) ratio by gas chromatography and 18:2 or 18:3 oxylipins by reversed phase-high performance liquid chromatography were determined. The viable cells, acidification activity and 18:2/16:0 or 18:3/ 16:0 ratio decreased as the storage time increased. The survival, acidification activity and 18:2/16:0 or 18:3/16:0 ratio were greatest for the freeze-dried strain held in vacuum-sealed aluminium foil at 4 °C. The 18:2/16:0 or 18:3/16:0 ratio decrease was correlated with the accumulation of 18:2 or 18:3 oxylipins during storage in glass tubes. Hydroperoxy PUFAs, hydroxy PUFAs, divinyl ether PUFAs and oxo PUFAs were the main oxylipins identified. A large decrease in the 18:2/16:0 or 18:3/16:0 ratio and a rapid accumulation of oxylipins during storage might be enough to cause high cell death and loss of metabolic activity. These results provide further experimental support for the hypothesis that lipid oxidation and survival or activity of freeze-dried bacteria might be related