Search results for " Fermentation"

Thermophilic hydrogen production from cellulose with rumen fluid enrichment cultures: Effects of different heat treatments

2011

Elevated temperatures (52, 60 and 65 °C) were used to enrich hydrogen producers on cellulose from cow rumen fluid. Methanogens were inhibited with two different heat treatments. Hydrogen production was considerable at 60 °C with the highest H2 yield of 0.44 mol-H2 mol-hexose -1 (1.93 mol-H2 mol-hexose-degraded-1) as obtained without heat treatment and with acetate and ethanol as the main fermentation products. H2 production rates and yields were controlled by cellulose degradation that was at the highest 21%. The optimum temperature and pH for H2 production of the rumen fluid enrichment culture were 62 °C and 7.3, respectively. The enrichments at 52 and 60 °C contained mainly bacteria from …

Application of MALDI-TOF-MS and nested SAPD-PCR for discrimination ofOenococcus oeniisolates at the strain level

2015

Oenococcus oeni is the most important lactic acid bacterium during vinification and is frequently used as a commercial starter culture for malolactic fermentation. Since different strains exhibit a high heterogeneity concerning wine-related physiological characteristics, reliable methods for their differentiation at the strain level are needed, especially for the development of starter cultures. Microbial identification by using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) has increased over the last few years. In the present study, we used MALDI-TOF-MS for the differentiation of 11 O. oeni isolates originating from 5 different wine-growing reg…

Grape pulp, grape pips and their mixture: Novel substrates or supports for solid state fermentation

1997

Grape marc, comprising of grape pulp and grape pips, is generated in high quantities during ethanol production, but has no significant commercial value. The components of the grape marc, individually or in combination, can serve as substrate or support in solid state fermentation. The potential benefits of sieved fractions (800-3150 µm particle size) was, therefore, evaluated using Trichoderma viride, with or whithout enrichment. Based on sorption isotherm profiles, grape pulp showed the best performance, though its ability to promote biomass formation was the lowest. The latter could be improved by enrichment with glucose. It, thus, offers potential as a reusable support. Grape pips promot…

The effect of Pediococcus acidilactici and Lactobacillus sakei on biogenic amines formation and free amino acid profile in different lupin during fer…

2016

Abstract The effect of Pediococcus acidilactici and Lactobacillus sakei strains on biogenic amines (BAs) formation during submerged and solid state fermentation of Lupinus luteus and Lupinus angustifolius was analysed. The composition of lupin seeds was evaluated and the influence of fermentation on free amino acid (FAA) profile was investigated. The highest protein and carbohydrate contents were found in L. luteus var. ‘Vilciai’, the highest carbohydrate contents – in L. angustifolius hybrid lines No. 1701 and No. 1800, and fat – in L. angustifolius hybrid lines No. 1700, No. 1703 and No. 1734. The interaction between the fermentation method, the bacterial strains used and lupin varieties …

Effect of fermented Helianthus tuberosus L. tubers on acrylamide formation and quality properties of wheat bread

2013

Abstract The main focus in this study was to investigate the effects on wheat bread safety and quality due to addition of Helianthus tuberosus L. (JA) tubers, fermented by different lactic acid bacteria (LAB) strains (Pediococcus acidilactici KTU05-7, Pediococcus pentosaceus KTU05-8, P. pentosaceus KTU05-9, Lactobacillus sakei KTU05-6, P. pentosaceus KTU05-10). We found experimentally that JA tubers fermented with LAB contained more L(+) than D(−) lactic acid, which resulted in safer products than by spontaneous treatment. The concentrations of biogenic amines in all analysed fermented JA products were far below levels causing a health risk, while the products fermented with LAB contained l…

Influence of nitrogen status in wine alcoholic fermentation

2019

Nitrogen is an essential nutrient for yeast during alcoholic fermentation. Nitrogen is involved in the biosynthesis of protein, amino acids, nucleotides, and other metabolites, including volatile compounds. However, recent studies have called several mechanisms that regulate its role in biosynthesis into question. An initial focus on S. cerevisiae has highlighted that the concept of "preferred" versus "non-preferred" nitrogen sources is extremely variable and strain-dependent. Then, the direct involvement of amino acids consumed in the formation of proteins and volatile compounds has recently been reevaluated. Indeed, studies have highlighted the key role of lipids in nitrogen regulation in…

Levan production byZymomonas mobilis cells. Attached to plaited spheres

1997

In this work, an immobilization method for polymer-levan production by a non-flocculating Z mobilis culture was developed. The extent of cell attachment to the stainless steel wire surface, culture growth and product synthesis were described. It was established that during short-term passive immobilization of non-flocculating Z mobilis cells on a stainless steel wire surface, sufficient amounts of biomass for proper levan and ethanol fermentation could not be obtained. Adherence of cells was improved by pressing the paste-like biomass within stainless steel spheres knitted from wire with subsequent dehydration. Biomass fixed in metal spheres was used for repeated batch fermentation of levan…

Ethanol production improvement in Zymomonas mobilis by supplementation of fructan-cleaving enzymes on sucrose containing substrates

2010

Yeast interaction on Chardonnay wine composition: Impact of strain and inoculation time.

2022

Abstract It is of great importance to understand the molecular characteristics and substantial chemical transformations due to yeast-yeast interaction. Non-targeted metabolomics was used to unravel must in fermentation composition, inoculated with non-Saccharomyces (NS) yeasts and Saccharomyces cerevisiae (S) for sequential fermentation. ultrahigh-resolution mass spectrometry was able to distinguish thousands of metabolites and provides deep insights into grape must composition allowing better understanding of the yeast-yeast interactome. The dominance of S, characterized by a metabolic richness not found with NS, is dependent on inoculation time and on the yeast species present. Co-inocula…

Influence of Mannaproteins from Yeast on the Aroma Intensity of a Model Wine

1994

Abstract The influence of mannaproteins released from yeast cell walls during alcoholic fermentation on the volatility of aroma substances was investigated in a model wine. After the characterization of macromolecules (substrates), two techniques have been used to study the interactions with aroma compounds: headspace analysis and an equilibrium dialysis method. The assumed effects of these macromolecules from yeasts on the fixation of volatile compounds were demonstrated. The physico-chemical interactions between aroma substances and mannaproteins depended on the nature of volatile compounds. Protein concentration in substrates was an important factor in their binding capacity. The retenti…