Search results for "fermentation"
showing 10 items of 746 documents
Immobilisation increases yeast cells' resistance to dehydration-rehydration treatment.
2014
This study was performed with the goal of revealing if the dehydration procedure used in our new immobilisation method noticeably decreases the viability of yeast cells in immobilised preparations. Various yeasts were used in this research: Saccharomyces cerevisiae cells that were rather sensitive to dehydration and had been aerobically grown in an ethanol-containing medium, a recombinant strain of S. cerevisiae grown in aerobic conditions which were completely non-resistant to dehydration and an anaerobically grown bakers' yeast strain S. cerevisiae, as well as a fairly resistant Pichia pastoris strain. Experiments performed showed that immobilisation of all these strains essentially incre…
Use of gases to improve survival of Bifidobacterium bifidum by modifying redox potential in fermented milk
2011
The aim of this work was to study the effect of the oxidoreduction potential, modified using gas, on the growth and survival of a probiotic strain, Bifidobacterium bifidum, and 2 yogurt strains, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. Three fermented milks were manufactured with an initial oxidoreduction potential value adjusted to +440 mV (control milk), +350 mV (milk gassed with N(2)), and -300 mV [milk gassed with N(2) plus 4% (vol/vol) H(2) (N(2)-H(2))]. Acidification profiles, growth during milk fermentation and survival during storage at 4 °C for 28 d were determined. This study showed that fermented probiotic dairy products made from milk gassed with…
In vivo application and dynamics of lactic acid bacteria for the four-season production of Vastedda-like cheese.
2014
article Twelve lactic acid bacteria (LAB), previously selected in vitro (Gaglio et al., 2014), were evaluated in situ for their potential to act as starter cultures for the continuous four-season production of Vastedda-like cheese, made with raw ewes' milk. The strains belonged to Lactobacillus delbrueckii, Lactococcus lactis subsp. cremoris, Leuconostoc mesenteroides subsp. mesenteroides and Streptococcus thermophilus .L AB werefirst inoculated in multiple-strain combinations on the basis of their optimal growth temperatures in three process conditions which differed for milk treatment and medium for strain development: process 1, growth of strains in the optimal synthetic media and pasteu…
Cell surface properties affect colonisation of raw milk by lactic acid bacteria at the microstructure level
2010
Cell localisation in the matrix microstructure of fermented food is important for microbial activity and ripening. To evaluate the importance of physicochemical factors in these phenomena, the physicochemical behaviour of four strains of lactic acid bacteria were investigated after inoculation of raw milk or milk fractions. To discriminate between physicochemical and metabolic properties, media were (i) rapidly acidified to avoid cell division or (ii) bacteria were allowed to ferment milk. To evaluate the impact of milk components, cells were dispersed in protein or fatty globule fractions. From two Lactococcus lactis subsp. lactis biovar. diacetylactis strains selected from their different…
A novel and simple method for the purification of extracellular levansucrase from Zymomonas mobilis.
2003
A new and simple method for the purification of extracellular levansucrase from Zymomonas mobilis from highly viscous fermentation broth was developed. After incubation of the fermentation broth with a fructose-polymer cleaving enzyme preparation (Fructozyme, Novozymes, DK) for 48 h, levansucrase precipitated as aggregates and was redissolved in a 3 M urea solution. By ongoing size-exclusion chromatography on Sephacryl S-300 the final levansucrase preparation was purified 100-fold and exhibited a specific activity of 25-35 U/mg(protein). The levansucrase was stable in 3 M urea solution for at least four months without inactivation. To maximize the enzyme yield the dynamic changes of extrace…
Two Methods for Highlighting the Influence of Sugars Type on Fermentation Processes Produced by Staphylococcus Carnosus and Lactobacillus Curvatus
2011
Purpose of this paper is to establish the influence of different types of sugars on fermentation processes found in the meat industry. In the analysis used a mixture of bacteria (Lactobacillus curvatus and Staphylococcus carnosus ), and the types of sugars were used lactose, lactulose, sucrose and two types of glucose syrup. To highlight the speed with which the fermentation process takes place, the variation in pH for the environment and the amount of energy released during biotechnological processes was measured.
Sugar beet diffusion juice and syrup as media for ethanol and levan production byZymomonas mobilis
1999
Abstract Sugar beet is an important crop cultivated widely in Europe. Roots contain up to 6–9 t/ha of fermentable sugar. Our laboratory is targeting to investigate the production possibilities of ethanol and levan by Zymomonas mobilis bacteria, using sugar beet juice or their syrup as raw material. The Z.mobilis strain 113 “S”;, selected in our institute, produces simultaneously with ethanol up to 40–70 g/1 fructose polymer levan in sucrose medium. It was established that Z.mobilis can convert sucrose into ethanol and levan in batch fermentation using natural sugar beet diffusion juice, without additives of mineral salts and growth factors. Syrup obtained in sugar industrial production by c…
Characterisation and detection of spoilage mould responsible for black spot in dry-cured fermented sausages.
2015
Moulds responsible for black spot spoilage of dry-cured fermented sausages were characterised. For this purpose, samples were taken from those dry-cured fermented sausages which showed black spot alteration. Most of the mould strains were first tentatively identified as Penicillium spp. due to their morphological characteristics in different culture conditions, with one strain as Cladosporium sp. The Cladosporium strain was the only one which provoked blackening in culture media. This strain was further characterised by sequencing of ITS1-5.8S-ITS2 rRNA and β-tubulin genes. This mould strain was able to reproduce black spot formation in dry-cured fermented sausage 'salchichon' throughout th…
The Saccharomyces cerevisiae flavodoxin-like proteins Ycp4 and Rfs1 play a role in stress response and in the regulation of genes related to metaboli…
2011
SPI1 is a gene whose expression responds to many environmental stimuli, including entry into stationary phase. We have performed a screening to identify genes that activate SPI1 promoter when overexpressed. The phosphatidylinositol- 4-phosphate 5-kinase gene MSS4 was identified as a positive activator of SPI1. Another SPI1 transcriptional regulator isolated was the flavodoxin-like gene YCP4. YCP4 and its homolog RFS1 regulate the expression of many genes during the late stages of growth. The double deletion mutant in YCP4 and its homolog RFS1 has an impact on gene expression related to metabolism by increasing the expression of genes involved in hexose transport and glycolysis, and decreasi…
A natural strategy to improve the shelf life of the loaf bread against toxigenic fungi: The employment of fermented whey powder.
2019
Whey powders are used as food ingredients in many applications, from bakery goods, soups and sauces to baby food. The objective of the study was to evaluate the antifungal property of a wheybased medium (WM) fermented by lactic acid bacteria. The antifungal activity of the WM was evaluated using antifungal tests on solid and liquid media. MIC and MFC ranged from 15.6 to 250 mg/ mL and 62.5 to 250 mg/mL, respectively. Using fermented WM for dough preparation produced a reduction of Penicillium expansum growth of 0.5–0.6 log CFU/g and an improvement in shelf life of 1–2 days in relation to control bread.