Explore the vast range of titles available.

Purpose To screen endophytic Bacillus producing volatile organic compounds (VOCs) with antifungal activity, and to explore their biocontrol properties toward the growth and pathogenicity of Curvularia lunata . Methods Two-sealed-base-plate assays were used to estimate the antifungal activities of Bacillus strains against C. lunata . Conjoint analysis of solid-phase microextraction gas chromatography-mass spectrometry and antagonistic experiments were used to identify the VOCs responsible for the antifungal activity. Effects of individual synthetic VOCs were analyzed along with reactive oxygen species (ROS) accumulation in C. lunata conidia. After exposure to individual VOCs, conidia were also sprayed onto maize leaves to evaluate their pathogenicity. Expression levels of virulence-related genes in C. lunata mycelium following exposure to VOCs were analyzed using quantitative real-time PCR. Results Among the ten endophytic Bacillus strains and two plant growth-promoting rhizobacterial (PGPR) strains, only B. subtilis strain DZSY21 strongly inhibited the growth of C. lunata by producing VOCs. 2-Methylbutyric acid, 2-heptanone, and isopentyl acetate produced by strain DZSY21 showed inhibitory effects on the mycelia growth and conidial sporulation of C. lunata . 2-Heptanone and isopentyl acetate also repressed the germination of conidia and the expression levels of virulence-related genes in C. lunata mycelium. Moreover, isopentyl acetate strongly enhanced the accumulation of intracellular ROS in conidia. The disease indexes of maize leaves sprayed with VOC-treated C. lunata conidia were reduced from 60.52 to 26.64%. Conclusion Endophytic B. subtilis strain DZSY21 displayed the potential to control C. lunata by producing VOCs, especially 2-heptanone and isopentyl acetate.

Pheromones are chemical messengers that trigger stereotyped behaviors and/or physiological processes in individuals of the same species. Recent reports suggest that pheromones can modulate behaviors not directly related to the pheromonal message itself and contribute, in this way, to behavioral plasticity. We tested this hypothesis by studying the effect of pheromones on sucrose responsiveness and habituation in honey bees. We exposed workers to three pheromone components: geraniol, which in nature is used in an appetitive context, and isopentyl acetate (IPA) and 2-heptanone (2H), which signal aversive situations. Pheromones associated with an aversive context induced a significant decrease of sucrose responsiveness as 40% and 60% of bees exposed to IPA and 2H, respectively, did not respond to any sucrose concentration. In bees that responded to sucrose, geraniol enhanced sucrose responsiveness while 2H, but not IPA, had the opposite effect. Geraniol and IPA had no effect on habituation while 2H induced faster habituation than controls. Overall, our results demonstrate that pheromones modulate reward responsiveness and to a lower degree habituation. Through their effect on sucrose responsiveness they could also affect appetitive associative learning. Thus, besides conveying stereotyped messages, pheromones may contribute to individual and colony-level plasticity by modulating motivational state and learning performances.

Honey bees play a crucial role in pollination, and in performing this critical function, face numerous threats from predators and parasites during foraging and homing trips. Back in the nest, their defensive behavior drives some individuals to sacrifice themselves while fighting intruders with their stingers or mandibles. During these intense conflicts, bees release alarm pheromone to rapidly communicate with other nest mates about the present danger. However, we still know little about why and how alarm pheromone is used in plant–pollinator–predator interactions. Here, we review the history of previously detected bee alarm pheromones and the current state of the chemical analyses. More new components and functions have been confirmed in honey bee alarm pheromone. Then, we ask how important the alarm pheromones are in intra- and/or inter-species communication. Some plants even adopt mimicry systems to attract either the pollinators themselves or their predators for pollination via alarm pheromone. Pheromones are honest signals that evolved in one species and can be one of the main driving factors affecting co-evolution in plant–pollinator–predator interactions. Our review intends to stimulate new studies on the neuronal, molecular, behavioral, and evolutionary levels in order to understand how alarm pheromone mediates communication in plant–pollinator–predator interactions.

Primer and releaser pheromones are molecules used for communication that induce species-specific responses. In contrast to primer pheromones, it is not known whether the quicker-acting releaser pheromones can affect brain gene expression. We show here that isopentyl acetate (IPA), a releaser pheromone that communicates alarm in honey bees, not only provokes a quick defensive response but also influences behavior for a longer period of time and affects brain gene expression. Exposure to IPA affected behavioral responsiveness to subsequent exposures to IPA and induced the expression of the immediate early gene and transcription factor c-Jun in the antennal lobes. Our findings blur the long-standing distinction between primer and releaser pheromone and highlight the pervasiveness of environmental regulation of brain gene expression.

In the honeybee, isopentyl acetate and 2-heptanone are described as alarm substances. We asked whether both substances have a similar role by testing the effect of their exposure on the appetitive proboscis extension reflex and on the aversive stinging reflex. In the appetitive context of sucrose stimulation no differences were found between isopentyl acetate and 2-heptanone. Small amounts of isopentyl acetate or 2-heptanone (3 µl of 1:9 dilution) yielded a response similar to that of a non-exposed control. Larger amounts of both substances (125 µl of 1:9 dilutions) as well as mixtures led to a decrease of responsiveness to sucrose. In the aversive context of electrical stimulation, significant differences between isopentyl acetate and 2-heptanone were found. Exposure to a small amount of isopentyl acetate (3 µl of 1:9 dilution) or to a large amount of 2-heptanone (125 µl of 1:9 dilution) led to an increase of responsiveness to the electric shock. Larger quantities of isopentyl acetate (125 µl of 1:9 dilution) decreased the responsiveness to the shock. 2-Heptanone never decreased the responsiveness to the shock. Our results indicate that isopentyl acetate and 2-heptanone have different functions even if both are capable of evoking deterrent responses in a defensive context.

The effects of the addition of two hydrocolloids--locust bean (LBG) and xanthan gums--at two concentrations (0.2 and 0.5%, w/v) on the intensity of the aroma of limonene and of isopentyl acetate solutions was studied using the pairwise ranking test. Previously, the rheological behaviour of the studied gums was analysed, finding that while LBG solutions were slightly pseudoplastic at the lower concentration and more so at the higher one, the xanthan solutions were clearly pseudoplastic at both concentrations. Addition of 0.2% LBG did not alter the limonene aroma intensity perceived, but on adding 0.5% LBG, above the coil overlap concentration (c*), the decrease in aroma intensity was significant. Addition of xanthan gum at any concentration did not modify the limonene aroma intensity perceived by judges, which can be attributed to the low value of c* for solutions of this gum. No difference in isopentyl acetate aroma was found among samples.[PUBLICATION ABSTRACT]

Volatile compounds produced by yeast during fermentation greatly influence the organoleptic qualities of wine. We developed a model to predict the combined effects of initial nitrogen and phytosterol content and fermentation temperature on the production of volatile compounds. We used a Box–Behnken design and response surface modeling to study the response of Lalvin EC1118® to these environmental conditions. Initial nitrogen content had the greatest influence on most compounds; however, there were differences in the value of fermentation parameters required for the maximal production of the various compounds. Fermentation parameters affected differently the production of isobutanol and isoamyl alcohol, although their synthesis involve the same enzymes and intermediate. We found differences in regulation of the synthesis of acetates of higher alcohols and ethyl esters, suggesting that fatty acid availability is the main factor influencing the synthesis of ethyl esters whereas the production of acetates depends on the activity of alcohol acetyltransferases. We also evaluated the effect of temperature on the total production of three esters by determining gas–liquid balances. Evaporation largely accounted for the effect of temperature on the accumulation of esters in liquid. Nonetheless, the metabolism of isoamyl acetate and ethyl octanoate was significantly affected by this parameter. We extended this study to other strains. Environmental parameters had a similar effect on aroma production in most strains. Nevertheless, the regulation of the synthesis of fermentative aromas was atypical in two strains: Lalvin K1M® and Affinity™ ECA5, which produces a high amount of aromatic compounds and was obtained by experimental evolution.

Ice wine is produced from concentrated grape juice obtained by the natural freezing and pressing of grapes. The high sugar content of this juice has an impact on fermentation. To investigate the impact of the initial sugar concentration on the fermentation of ice wine, the initial sugar concentration of Vidal ice grape juice was adjusted to 370, 450, 500 and 550 g/L by the addition of glucose. The fermentation process was conducted at a temperature of 18 °C with Zymaflore ST yeast. To ensure optimal fermentation, the yeast assimilable nitrogen (YAN) in the grape juice was adjusted to 350 mg/L using a commercial nitrogen source. The initial sugar concentrations (370, 450, 500, and 550 g/L) were significantly negatively correlated with the number of viable yeast during active fermentation, the total consumption of sugar and YAN, and ethanol production (130.26, 117.83, 106.14, and 90.85 g/L) but positively correlated with the production of acetic acid (0.82–2.86 g/L) and acetaldehyde. Fermentation with initial sugar concentrations ≥ 500 g/L (500 and 550 g/L) produced ethanol (106.14 and 90.85 g/L) and excessive acetic acid (2.14 and 2.86 g/L), inhibited the esterification of n -butanol and n -hexanol, and promoted the production of isopentanol, isoamyl acetate, diethyl succinate, ethyl hexanoate and ethyl octanoate while increasing the production of 2-phenylethanol and isobutanol. The initial sugar concentration affected the production of glycerol, isobutanol, ethyl acetate, and diethyl succinate, but it did not affect the final contents of the ice wine. This study examined fermentation dynamics, including substrate consumption, yeast cell production, and the production of important metabolites such as ethanol, acetic acid, higher alcohols, and esters. Appropriate initial concentrations of YAN and sugar (below 500 g/L) and a relatively high ratio of glucose to fructose (between 1:1 and 1.7:1) is preferable for effective ice wine fermentation.

This study investigates the impact of wet fermentation on flavor volatiles and sensory quality of coffee beans and beverage. Pulped coffee beans were kept underwater for 36 h before air-drying and roasting, and volatiles in the beans were characterized by solid-phase microextraction and gas chromatography–mass spectrometry. A total of 79 volatiles were identified. Fermented roasted beans had higher concentrations of ethanol, isoamyl alcohol, 3-methylbutanal, benzaldehyde, acetaldehyde, and ethyl acetate compared with mechanically processed (no fermentation) beans; whereas, ketones, pyrazines, pyrroles, pyridines, furans and sulfides were not significantly different between the two treatments. Coffee made with fermented beans was rated significantly higher in flavor, aroma, acidity, body and uniformity scores with noted fruity aroma compared with beverage made with mechanically processed beans in sensory evaluation (cup test) by a 3 Q-Grade Coffee Certification Panel. The findings demonstrated wet fermentation played an important role in coffee flavor, aroma and sensory quality.