Alternative hormone-free reproduction management of a dairy sheep flock disrupts the farm's annual feeding system calendar and its associated strategies.

Hormone-free (HF) reproduction in dairy sheep is a way to meet current societal demands, but it requires being prepared for collateral impacts on related system components. The efficiency of HF practices (e.g., using the male effect for estrus induction and synchronization) is uncertain compared with hormonal treatment (HT). For example, these practices can lead to higher variability in the flock physiological stage patterns throughout the year, which has direct consequences for feeding regimens. The objective of this work was to simulate the impacts of HF reproduction management, including artificial insemination (AI), on the temporal distribution of productive performance and nutritional requirements of a conventional dairy sheep flock. Using the REPROsheep2.0 model, 6 scenarios were compared over one typical production season for the same flock (n = 597 Lacaune ewes) intensively reared in the Roquefort region of France. These scenarios depicted reproduction with HT and AI in mid-May (Early); HT and AI in July (Summer Late); HT and AI in November (Autumn Late); and their HF versions (HF-Early; HF-Summer Late, and HF-Autumn Late, respectively). In all HF scenarios, a reduction in the number of ewes lambing and consequently in the annual milk production of the farm was observed (-1 to -7%). This affected annual performance with a subsequent decrease of total annual nutritional requirements (-2 to -6%). The HF scenarios resulted in a staggering of lambing events with a 7- to 14-d shift in the appearance of milk production peaks and related nutritional requirements compared with the HT scenarios. Transitioning from conventional to HF reproduction management, while preserving AI, would increase farm workload, lengthen milking period operations, and necessitate a readjustment of feeding management strategies with regard to available feed resources. Depending on the production season, the observed delay in the distribution of nutritional requirements could be either an attractive or an unfavorable outcome for farmers. The delay may be concordant, for example, with the recently observed impacts of climate change on seasonal forage availability in Mediterranean regions (less spring herbage production and warmer temperatures) that are affecting farmers' decision-making about the most efficient use of forage and feed resources.

Effect of a fungal chitosan preparation on Brettanomyces bruxellensis, a wine contaminant.

AIM: To investigate the action mechanisms of a specific fungal origin chitosan preparation on Brettanomyces bruxellensis. METHODS AND RESULTS: Different approaches in a wine-model synthetic medium were carried out: optical and electronic microscopy, flow cytometry, ATP flow measurements and zeta potential characterization. The inactivation effect was confirmed. Moreover, fungal origin chitosan induced both physical and biological effects on B. bruxellensis cells. Physical effect led to aggregation of cells with chitosan likely due to charge interactions. At the same time, a biological effect induced a leakage of ATP and thus a viability loss of B. bruxellensis cells. CONCLUSIONS: The antimicrobial action mode of chitosan against B. bruxellensis is not a simple mechanism but the result of several mechanisms acting together. SIGNIFICANCE AND IMPACT OF THE STUDY: Brettanomyces bruxellensis, a yeast responsible for the production of undesirable aromatic compounds (volatile phenols), is a permanent threat to wine quality. Today, different means are implemented to fight against B. bruxellensis, but are not always sufficient. The chitosan of fungal origin is introduced as a new tool to control B. bruxellensis in winemaking and has poorly been studied before for this application.

A mathematical model of the link between growth and L-malic acid consumption for five strains of Oenococcus oeni.

In winemaking, after the alcoholic fermentation of red wines and some white wines, L-malic acid must be converted into L-lactic acid to reduce the acidity. This malolactic fermentation (MLF) is usually carried out by the lactic acid bacteria Oenococcus oeni. Depending on the level of process control, selected O. oeni is inoculated or the natural microbiota of the cellar is used. This study considers the link between growth and MLF for five strains of O. oeni species. The kinetics of growth and L-malic acid consumption were followed in modified MRS medium (20 °C, pH 3.5, and 10 % ethanol) in anaerobic conditions. A large variability was found among the strains for both their growth and their consumption of L-malic acid. There was no direct link between biomass productivities and consumption of L-malic acid among strains but there was a link of proportionality between the specific growth of a strain and its specific consumption of L-malic acid. Experiments with and without malic acid clearly demonstrated that malic acid consumption improved the growth of strains. This link was quantified by a mathematical model comparing the intrinsic malic acid consumption capacity of the strains.

Isolation of Bacillus spp. from Thai fermented soybean (Thua-nao): screening for aflatoxin B1 and ochratoxin A detoxification.

AIMS: To study the interaction between Bacillus spp. and contaminating Aspergillus flavus isolated strains from Thai fermented soybean in order to limit aflatoxin production. To study the detoxification of aflatoxin B(1) (AFB(1)) and ochratoxin A (OTA) by Bacillus spp. in order to find an efficient strain to remove these toxins. METHODS AND RESULTS: One A. flavus aflatoxin-producing strain and 23 isolates of Bacillus spp. were isolated from soybean and fresh Thua-nao collected from the north of Thailand. Inhibition studies of A. flavus and A. westerdijkiae NRRL 3174 (reference strain) growth by all isolates of Bacillus spp. were conducted by dual culture technique on agar plates. These isolates were also tested for AFB(1) and OTA detoxification ability on both solid and liquid media. Most of the strains were able to detoxify aflatoxin but only some of them could detoxify OTA. CONCLUSIONS: One Bacillus strain was able to inhibit growth of both Aspergillus strains and to remove both mycotoxins (decrease of 74% of AFB(1) and 92.5% of OTA). It was identified by ITS sequencing as Bacillus licheniformis. The OTA decrease was due to degradation in OTalpha. Another Bacillus strain inhibiting both Aspergillus growth and detoxifying 85% of AFB(1) was identified as B. subtilis. AFB(1) decrease has not been correlated to appearance of a degradation product. SIGNIFICANCE AND IMPACT OF THE STUDY: The possibility to reduce AFB(1) level by a strain from the natural flora is of great interest for the control of the quality of fermented soybean. Moreover, the same strain could be a source of efficient enzyme for OTA degradation in other food or feeds.

Black aspergilli and ochratoxin A production in French vineyards.

A survey on the occurrence on grape of black Aspergillus species and their capability to produce ochratoxin A (OTA) was conducted in France over three years (2001-2003) in 10 vineyards from four winemaking regions with different geographical locations and climatic conditions. During 2001 and 2002, from setting to harvest, the total numbers of fungal isolates were respectively 721 and 711 increasing in 2003 to reach 1035. The Aspergillus genus was essentially represented by Section Nigri (99%) and it was predominant (80%+/-4.6) when compared to Penicillium (20%+/-4.6). Regardless of sampling year, 32.5% (+/-sigma=1.26) of the fungal isolates were OTA producers and 93% (+/-sigma=2.65) belonging to black aspergilli. The ochratoxigenic potential of the isolates and their occurrence on grapes revealed that Aspergillus carbonarius was the main OTA producer (up to 37.5 mug/g). At harvest time, the fungal population was maximal and this was the most critical period influencing OTA contamination. Grapes from Languedoc-Roussillon region were most infested with ochratoxigenic fungi and had the highest concentrations of OTA (up to 2.8 ng/g).

Conidia of black aspergilli as new biological adsorbents for ochratoxin A in grape juices and musts.

Biological removal of ochratoxin A (OTA) by living and heat-treated dead conidia of black Aspergillus isolates representing the species Aspergillus niger, Aspergillus carbonarius, and Aspergillus japonicus in synthetic and natural grape juices was found to be a two-stage phenomenon. Several lines of evidence suggest that the first observed stage was passive, metabolism was not required, and OTA adsorption on conidia of black aspergilli could be involved. This removal was fast, without delay just after conidial inoculation both in synthetic and natural grape juices. Moreover, even nonviable, heat-treated conidia were capable of removing OTA. Finally, no OTA degradation products were detected. In the second observed stage, removal of OTA was linked to degradation by live conidia only. Ochratoxin alpha, a degradation product of OTA, was detected in the medium after incubation for 30 and 14 h for biseriate (A. niger and A. carbonarius) and uniseriate (A. japonicus) black aspergilli, respectively, when well-developed mycelium appeared. Comparisons between the three black Aspergillus isolates tested showed that A. carbonarius detoxified grape juice most effectively. However, this species often produces OTA. A. niger and A. japonicus isolates were also effective and because those species are not systematically OTA producers, they could be interesting for further OTA detoxification processes in grape juices and musts.

Ochratoxin A removal in synthetic and natural grape juices by selected oenological Saccharomyces strains.

AIMS: To assess, for the first time the efficiency in removing ochratoxin A (OTA) from laboratory medium [yeast peptone glucose (YPG)], synthetic grape juice medium (SGM) and natural grape juice by viable and dead (heat and acid-treated) oenological Saccharomyces strains (five S. cerevisiae and one S. bayanus) compared with a commercial yeast walls additive. METHODS AND RESULTS: Levels of OTA during its interaction with six oenological Saccharomyces strains (five S. cerevisiae and one S. bayanus) or with a commercial yeast walls additive in YPG medium, in SGM or in natural grape juices was assessed by HPLC after appropriate extraction methods. A significant decrease of OTA levels in YPG medium and SGM was observed for many of the growing strains reaching a maximum of 45%, but no degradation products were detected. With both heat and acid pretreated yeasts, OTA removal was enhanced, indicating that adsorption, not catabolism, is the mechanism to reduce OTA concentrations. Adsorption was also improved when the yeast concentration was increased and when the pH of the medium was lower. Approximately 90% of OTA was bound rapidly within 5 min and up to 72 h of incubation with heat-treated cells of either S. cerevisiae or S. bayanus. A comparative study between heat-treated cells (HC) and commercial yeast walls (YW) (used as oenological additive), introduced at two different concentrations (0.2 and 6.7 g l(-1)) in an OTA-contaminated grape juice, showed the highest efficiency by HC to adsorb rapidly within 5 min the total amount of the mycotoxin. CONCLUSIONS: Oenological S. cerevisiae and S. bayanus were able to remove ochatoxin A from synthetic and natural grape juices. This removal was rapid and improved by dead yeasts having more efficiency than commercial yeast walls. SIGNIFICANCE AND IMPACT OF THE STUDY: The efficiency of heat-treated yeasts to remove OTA gives a new hope for grape juice and must decontamination avoiding negative impacts on human health.

Characterization of the metabolic shift of Saccharomyces bayanus var. uvarum by continuous aerobic culture.

Saccharomyces bayanus, being of interest for wine-making, is not as well known as S. cerevisiae and, due to many changes in the yeast classification, accurate data concerning its metabolic activity are difficult to find. In order to produce this yeast as an active dry yeast to be used as a starter in wine-making, its sensitivity to glucose was determined as the objective of our work. Using the pulse technique in continuous culture, it was found that growth in a synthetic medium was not limited by vitamins or mineral salts. We determined the critical dilution rate of a continuous culture and performed an aerobic continuous culture, measuring the respiratory quotient on-line in order to observe the metabolic shift from respiratory to fermentative metabolism. The S. bayanus var. uvarum strain studied was Crabtree-positive (glucose-sensitive) but had a weaker respiratory capacity than S. cerevisiae since the dilution rate of the metabolic shift was only 0.15 h(-1). These new data provide essential information for the biomass production of this yeast strain for wine-making.

Stoichiometry of diauxic growth of a xylanase-producing Bacillus strain.

In this work, the establishment of material balances and stoichiometry of the growth of Bacillus sp. was undertaken. This strain produces high quantities of a xylanase suitable for use as bleach boost agent in chlorine-free bleaching sequences of paper pulp. As carbon dioxide plays an important role as a growth factor, bacterial growth in two fermentations, one fed with air and another fed with carbon-dioxide-enriched air, were compared. For this purpose, a method permitting the determination of the consumption of the two carbon sources, xylan and peptone, was proposed. The material balances revealed that in both cases, the bacteria first use peptone as their carbon source, and then xylan in the second part of the growth phase. The aerated culture showed diauxic growth on these two substrates, whereas carbon-dioxide-enriched air caused disappearance of the metabolic adaptation phase, and rendered biomass production more economic. The fermentation fed with air needed 30% more xylan than the fermentation fed with carbon-dioxide-enriched air for the same quantity of biomass produced.

Oxygen effect on lactose catabolism by a Leuconostoc mesenteroides strain: modeling of general O2-dependent stoichiometry.

Lactose metabolism of a Leuconostoc mesenteroides strain was studied in batch cultures at a pH of 6.5 and 30 degrees C in 10 L of a modified MRS (De Man, Rogosa, Sharp) broth. The end products of this heterolactic bacterium were D-lactate, acetate, ethanol, and carbon dioxide. To test the effect of oxygen on their synthesis, the medium was sparged with different gases: nitrogen, air, and pure oxygen. When oxygen was available, oxygen uptake occurred, which caused a modification in acetate and ethanol production but not in lactate or carbon dioxide production; acetate plus ethanol together were produced in constant amounts, which were independent of the level of aeration. The influence of oxygen on end-product formation could be summed up by the general equation: lactose + x O(2) --> 2 D-lactate + (x + 0.1) acetate + (2 - x) ethanol + 2 CO(2). Maximal oxygen uptake (x = 2) was reached under a 120 L/h flow rate of pure oxygen. In addition, this equation provided useful information on the possible pathway of galactose catabolism by a heterofermentative microorganism.

Influence of pH, malic acid and glucose concentrations on malic acid consumption by Saccharomyces cerevisiae.

Malic acid consumption by Saccharomyces cerevisiae was studied in a synthetic medium. The extent of malic acid degradation is affected by its initial concentration, the extent and the rate of deacidification increased with initial malate concentration up to 10 milligrams. For malic acid consumption, an optimal pH range of 3-3.5 was found, confirming that non-dissociated organic acids enter S. cerevisiae cells by simple diffusion. A full factorial design has been employed to describe a statistical model of the effect of sugar and malic acid on the quantity of malate degraded (milligrams) by a given amount of biomass (milligrams). The results indicated that the initial malic acid concentration is very important for the ratio of malate consumption to quantity of biomass. The yeast was found to be most efficient at higher levels of malate.