Sugar Feed Rate Research Articles

Natural sugar feeding rates of Anopheles mosquitoes collected by different methods in western Kenya

Attractive targeted sugar baits (ATSBs) are a potential vector control tool that exploits the sugar-feeding behaviour of mosquitoes. We evaluated the sugar-feeding behaviour of Anopheles mosquitoes as part of baseline studies for cluster randomised controlled trials of ATSBs. Mosquitoes were collected indoors and outdoors from two villages in western Kenya using prokopack aspirations, malaise tent traps and ultraviolet (UV) light traps. Individual mosquitoes were subjected to the cold anthrone test to assess the presence of sugar. Overall, 15.7% of collected mosquitoes had fed on natural sugar sources. By species and sex, the proportion sugar-fed was 41.3% and 27.7% in male and female Anopheles funestus, 27.2% and 12.8% in male and female An. arabiensis, and 9.7% and 8.3% in male and female An. coustani, respectively. Sugar-feeding was higher in unfed than blood-fed mosquitoes and higher in male than gravid mosquitoes. Anopheles mosquitoes obtained sugar meals from natural sources during all physiological stages, whether they rest indoors or outdoors. These findings offer a potential avenue to exploit for the control of mosquitoes, particularly with the advent of ATSBs, which have been shown to reduce mosquito densities in other regions.

Sugar feeding by parasitoids inside and around vineyards varies with season and weed management practice

Feeding on sugar-rich resources dramatically prolongs lifespan and increases foraging performance in most parasitoids. The physiological and fitness effects of sugar feeding were studied in many parasitoid species under lab conditions, but far fewer studies examined them in the field. Even less is known about the environmental conditions that affect the prevalence of sugar feeding in natural parasitoid communities. Such information can guide planning of suitable habitats for these important biological control agents. We compared sugar feeding frequencies in parasitoid communities along four seasons, in wine-producing vineyards and in nearby natural plots, using qualitative anthrone tests. We also tested how the vineyards’ weed management practice (mechanical trimming or herbicide application) affected the parasitoids’ sugar feeding rates. Sugar feeding was significantly more common in the natural areas compared to the vineyards in all seasons. Sugar feeding rates were highest during spring and lowest in the winter. They were not consistently affected by weed management treatment, but increased with the number of flowering plant species, especially in spring. Our results suggest that parasitoids are limited by sugar sources in agricultural plots even when undisturbed by farming activities (during winter in our case), and that 'softer' weed management treatments do not necessarily improve their prospects for sugar feeding. A more targeted approach, of planting or preserving a higher richness of flowering plants throughout the seasons, may provide parasitoids with more sugar sources and thus support them in agricultural plots.

Frequent sugar feeding behavior by Aedes aegypti in Bamako, Mali makes them ideal candidates for control with attractive toxic sugar baits (ATSB).

BackgroundCurrent tools and strategies are not sufficient to reliably address threats and outbreaks of arboviruses including Zika, dengue, chikungunya, and yellow fever. Hence there is a growing public health challenge to identify the best new control tools to use against the vector Aedes aegypti. In this study, we investigated Ae. aegypti sugar feeding strategies in Bamako, Mali, to determine if this species can be controlled effectively using attractive toxic sugar baits (ATSB).MethodologyWe determined the relative attraction of Ae. aegypti males and females to a variety of sugar sources including flowers, fruits, seedpods, and honeydew in the laboratory and using plant-baited traps in the field. Next, we observed the rhythm of blood feeding versus sugar feeding activity of Ae. aegypti in vegetation and in open areas. Finally, we studied the effectiveness of spraying vegetation with ATSB on Ae. aegypti in sugar rich (lush vegetation) and in sugar poor (sparse vegetation) urban environments.Principal findingsMale and female laboratory sugar feeding rates within 24 h, on 8 of 16 plants offered were over 80%. The survival rates of mosquitoes on several plant sources were nearly as long as that of controls maintained on sucrose solution. In the field, females were highly attracted to 11 of 20 sugar sources, and 8 of these were attractive to males. Peak periods of host attraction for blood-feeding and sugar feeding in open areas were nearly identical and occurred shortly after sunrise and around sunset. In shaded areas, the first sugar-seeking peak occurred between 11:30 and 12:30 while the second was from 16:30 to 17:30. In a 50-day field trial, ATSB significantly reduced mean numbers of landing / biting female Ae. aegypti in the two types of vegetation. At sugar poor sites, the mean pre-treatment catch of 20.51 females on day 14 was reduced 70-fold to 0.29 on day 50. At sugar rich sites, the mean pre-treatment catch of 32.46 females on day 14 was reduced 10-fold to a mean of 3.20 females on day 50.ConclusionsThis is the first study to show how the vector Ae. aegypti depends on environmental resources of sugar for feeding and survival. The demonstration that Ae. aegypti populations rapidly collapsed after ATSB treatment, in both sugar rich and sugar poor environments, is strong evidence that Ae. aegypti is sugar-feeding frequently. Indeed, this study clearly demonstrates that Ae. aegypti mosquitoes depend on natural sugar resources, and a promising new method for vector control, ATSB, can be highly effective in the fight against Aedes-transmitted diseases.

Performance investigation of a pilot scale integrated aerobic–anaerobic baffle reactor for continuous ethanol production process under various sugar-feeding rates

Ethanol as the promising alternative fuel in Indonesia fights against cost competitiveness with fossil fuel due to low productivity using a conventional batch process. Therefore, the production of ethanol employing continuous fermentation process in which it acquires higher productivity was investigated. The investigation was done using uncontrolled continuous process in the integrated aerobic–anaerobic baffled reactor for 168–340 h at 30℃ and medium pH of 4–5. The substrate of sugarcane molasses–water was varied in three concentrations, i.e. 20, 30, and 45% w/w. The productivity was indicated by ethanol concentration in the effluent stream and sugar to ethanol conversion (fermentation efficiency). The result showed that average ethanol concentration of 20, 30, and 45% molasses was 50.43, 62.70, and 57.17 g/l, respectively. Further, the fermentation efficiencies were 87.2, 80.3, and 46.7% for each of the molasses concentrations. The productivity can be monitored as follows: 1.75 g/l h (20% molasses), 2.31...

Quantifying the mosquito’s sweet tooth: modelling the effectiveness of attractive toxic sugar baits (ATSB) for malaria vector control

BackgroundCurrent vector control strategies focus largely on indoor measures, such as long-lasting insecticide treated nets (LLINs) and indoor residual spraying (IRS); however mosquitoes frequently feed on sugar sources outdoors, inviting the possibility of novel control strategies. Attractive toxic sugar baits (ATSB), either sprayed on vegetation or provided in outdoor bait stations, have been shown to significantly reduce mosquito densities in these settings.MethodsSimple models of mosquito sugar-feeding behaviour were fitted to data from an ATSB field trial in Mali and used to estimate sugar-feeding rates and the potential of ATSB to control mosquito populations. The model and fitted parameters were then incorporated into a larger integrated vector management (IVM) model to assess the potential contribution of ATSB to future IVM programmes.ResultsIn the Mali experimental setting, the model suggests that about half of female mosquitoes fed on ATSB solution per day, dying within several hours of ingesting the toxin. Using a model incorporating the number of gonotrophic cycles completed by female mosquitoes, a higher sugar-feeding rate was estimated for younger mosquitoes than for older mosquitoes. Extending this model to incorporate other vector control interventions suggests that an IVM programme based on both ATSB and LLINs may substantially reduce mosquito density and survival rates in this setting, thereby substantially reducing parasite transmission. This is predicted to exceed the impact of LLINs in combination with IRS provided ATSB feeding rates are 50% or more of Mali experimental levels. In addition, ATSB is predicted to be particularly effective against Anopheles arabiensis, which is relatively exophilic and therefore less affected by IRS and LLINs.ConclusionsThese results suggest that high coverage with a combination of LLINs and ATSB could result in substantial reductions in malaria transmission in this setting. Further field studies of ATSB in other settings are needed to assess the potential of ATSB as a component in future IVM malaria control strategies.

Floral resources impact longevity and oviposition rate of a parasitoid in the field

1. The use of floral resource subsidies to improve herbivore suppression by parasitoids requires certain trophic interactions and physiological changes to occur. While the longevity and fecundity of parasitoids are positively affected by nectar subsidies in laboratory studies, the impacts of floral subsidies on the fecundity and longevity of freely foraging parasitoids have not been studied. 2. We studied the longevity and per capita fecundity of naturally occurring Diadegma insulare foraging in cabbage plots with and without borders of flowering buckwheat, Fagopyrum esculentum, as well as relationships between longevity, fecundity, sugar feeding and parasitism rates on larvae of the diamondback moth, Plutella xylostella. 3. Relative longevity was estimated by counting broken setae on the fringe of the forewing. Floral borders increased the longevity of males and females in adjacent cabbage plots. 4. The egg maturation rate of D. insulare was estimated by comparing egg loads of females collected early in the day with egg loads of females held without hosts in field cages throughout the day. Females in buckwheat cages matured 2.7 eggs per hour while females in control cages resorbed 0.27 eggs over the same time period. 5. The fecundity of females collected in the afternoon was estimated by comparing their actual egg load to the estimated egg load in the absence of oviposition for females in a given plot. Females foraging in buckwheat plots had marginally fewer eggs remaining in their ovaries, and laid marginally more eggs than females in control plots. Females from both treatments carried 30-60 eggs by the afternoon and therefore were time-limited rather than egg-limited. 6. Plots where a greater proportion of females had fed on sugar had longer-lived females. This suggests that feeding enhanced longevity of D. insulare. However, plots with longer-lived and more fecund females did not exhibit higher parasitism rates, although the power of these tests were low.

Industrial application of fuzzy control in bioprocesses.

In a bioprocess, for example a fermentation process, many biological reactions are always working in intracellular space and the control of such a process is very complicated. Bioprocesses have therefore been controlled by the judgment of the experts who are the skilled operators and have much experience in the control of such processes. Such experience is normally described in terms of linguistic IF-THEN rules. Fuzzy inference is a powerful tool for incorporating linguistic rules into computer control of such processes. Fuzzy control is divided into two types--direct fuzzy control of process variables, for example sugar feed rate and fermentation temperature, and indirect control via phase recognition. In bioprocess control the experts decide the value of controllable process variables such as sugar feed rate or temperature as output data from several state variables as input data. Fuzzy control is regarded as a computational algorithm in which the causal relationship between input and output data are incorporated. In Japan fuzzy control has already been applied to practical industrial processes such as production of pravastatin precursor and vitamin B2 and to the Japanese sake mashing process; these examples are reviewed. In addition, an advanced control tool developed from a study on fuzzy control, fuzzy neural networks (FNN), are introduced. FNN can involve complicated causality between input and output data in a network model. FNN have been proven to be applicable to a research in biomedicine, for example modeling of the complicated causality between electroencephalogram or gene expression profiling data and prognostic prediction. Successful results on this research will be also explained.

Fuzzy control of bioprocess in Japan

Process control of bioprocess has been carried out by the judgment of the experts, who are the skilled operators and have lots of experiences for the control of the process. In almost all cases, those experiences are described linguistic IF-THEN rules. Fussy inference is one of the powerful tools to incorporate the linguistic rules to the computer for process control. Fuzzy control are divided into two types; one is the direct fuzzy control of process variables such as sugar feed rate in fed-batch culture and fermentation temperature in batch operation. The other is the indirect control of bioprocess, in which at first the phase recognition is carried out by fuzzy inference and the control strategies constructed in each phase are used for the control of process variables. In Japan, the fuzzy control has already been applied to practical industrial productions, such as pravastatin precursor, vitamin B2, and Japanese sake mashing process. In this review, these industrial approaches of fuzzy control are introduced.

Optimization of feeding profile for baker's yeast production by dynamic programming

An optimal substrate feeding strategy for an industrial scale fed-batch fermenter is determined through iterative dynamic programming in order to maximize cell-mass production and to minimize ethanol formation. The objective function is maximized with respect to the sugar feed rate. The obtained optimal policy indicates considerable increase in yeast production achieved while minimizing the undesired by-product-ethanol.

Control of cell growth rate by sugar feeding based on CO 2 production rate

Sugar feeding based on the CO 2 production rate was investigated for the control of the cell growth rate during cephalosporin C fermentation in which sugar concentration was the growth limiting factor. The rates of cell growth and sugar consumption were apparently influenced by the sugar feed rate, as the sugar concentration in the broth was kept at approximately 1 g/ l during the cultivation. The ratio of the CO 2 production rate to the sugar consumption rate was maintained almost constant after 40 h cultivation. Stepwise alteration in sugar feed rate after the culture time of 50 h caused a change in the CO 2 production rate within 15 min. These results indicated that the CO 2 production rate could be used as an effective parameter of sugar consumption and cell growth rates. Consequently, a control strategy was developed that involved the control of sugar feed rate so that a CO 2 production rate profile corresponded to a preset standard profile. For the half the usual amount of inoculum, the sugar feeding control system enabled the cell concentration to increase faster to that in the usual inoculum. The cell concentration deviation during exponential growth phase among several batches, decreased to half using this sugar feeding control system compared to the culture without such control. These results indicated that the sugar feeding control system developed in this report was found to be efficient for control of cell growth.

Influence of plant abundance on nectar feeding by Aedes aegypti (Diptera: Culicidae) in southern Mexico.

The availability of flowering plants affected the sugar feeding rates of female Aedes aegypti (L.) in 4 areas of a small city in southern Mexico. The proportion of mosquitoes containing sugar varied from 8 to 21% in 4 areas in direct relation to blooming plant abundance. Human density was similar in the 4 areas (range, 3.9-5.4 per house), whereas the number of flowering plants per house increased on the outskirts (range, 3.1-5.4 plants per house). Equal proportions of sugar positive females were nulliparous or parous, indicating similar sugar feeding at any age. In addition, nearly 60% of positive females were at the Christophers stage II, indicating a greater need for flight fuel during the early stages of egg development. We conclude that Ae. aegypti feeds frequently on nectar and that this activity is modulated by nectar availability.

Mathematical modelling of industrial pilot-plant penicillin-G fed-batch fermentations.

Penicillin-G fermentation with industrial media in 1 m3 stirred tank bioreactors was studied. A model based on the Bajpai-Reuss model structure was developed. Under typical production conditions catabolite repression is nonidentifiable and extensive mycelium differentiation occurs. Thus, the original model was reformulated, neglecting glucose repression of penicillin production and including biomass autolysis. The multi-substrate nature of industrial media was critically analysed. By combining the two most important carbon substrates present, a simple and applicable model was obtained. Model predictions agreed well with experimental data and reproduced the general characteristics observed in the fermentations. The predictive power of the model was tested for fermentations with different sugar feed rate profiles and raw materials (corn-steep liquor and sugar syrup). Several aspects of parameter estimation and model development are discussed on the basis of direct experimental data inspection and a sensitivity analysis of model parameters.

Advanced control of glutathione fermentation process

A study was performed to understand the fermentation process for production of glutathione fermentation (GSH) with an improved strain of baker's yeast. Simultaneous utilization of sugar and ethanol has been found to be a key factor in the industrial process to produce GSH using Saccharomyces cerevisiae KY6186. Based on this observation, the optimal sugar feed profile for the fed-batch operation has been determined. A feedforward/feedback control system was developed to regulate the sugar feed rate so as to maximize GSH production yields. Using the feedforward/feedback control system and the on-line data of oxygen and ethanol concentration in exhaust gas, the successful scaleup to the production level was accomplished. An average of 40% improvement of glutathione production compared to a conventionally programmed control of exponential fed-batch operation was found in the new process.

Application of expert fuzzy controller in the penicillin fermentation processes

The expert fuzzy control system of the penicillin fermentation processes is developed in the paper which can recognize different fermentation phases and adopt related control strategies. Feed rates are controlled according to PH value and penicillin productive rate. The fuzzy control models of sugar feed rate are established. Finally, two illustrative examples are given to show that the control strategies developed is feasible and reliable for real plants.

Kinetics of ethanol production during the reactor feeding phase in constant feb‐batch fermentation of molasses

During the fermentor feeding phase in constant fed-batch ethanol fermentation of molasses, the ethanol production rates are constant and are correlated to the sugar feeding rates by a Monod-like equation. The parameters of this Monod-like correlation depend on the sugars concentration of the feeding mash. A model is proposed to explain the constancy of the ethanol production rate experimentally observed. From the Monod-like correlation it is possible to evaluate the maximum value of the mash feeding rate to be used in order to have a completely fermented medium just at the end of the feeding phase.

Sand flies (Diptera: Psychodidae) associated with visceral leishmaniasis in El Agamy, Alexandria Governorate, Egypt. II. Field behavior.

Behavioral patterns of Phlebotomus papatasi and langeroni were studied in El Agamy, a focus of visceral leishmaniasis in Alexandria Governorate, Egypt. Both species were nocturnally active in outdoor habitats from sunset to sunrise, with highest activity levels after midnight. Phlebotomus papatasi , a highly endophilic species, began entering houses directly after sunset; ingress was estimated at 17% before 2300 h and 83% from 2300 h to sunrise. Blood-engorgement rates inside houses were 75% for P. papatasi ( n = 2,238) and 52% for P. langeroni ( n = 23). Phlebotomus papatasi was gonotrophically discordant, as 14% of 222 indoor-collected, half-gravid females contained small, fresh blood meals. Phlebotomus papatasi rested inside houses during all stages of gonotrophic development, apparently with frequent ingress and egress. A total of 514 P. papatasi and 158 P. langeroni were tested for fructose by the anthrone technique. Sugar-feeding rates for both species inside houses, in different stages of blood digestion, ranged from 25 to 62%; ca. 60% of the freshly engorged females had fed on sugar. Outdoor rates were 32% for P. papatasi females, 55% for P. papatasi males and P. langeroni females, and 57% for male P. langeroni. Phlebotomus langeroni showed a greater attraction than P. papatasi to light traps and dog-baited traps. Behavioral differences between the 2 species are discussed in relation to potential for Leishmania transmission.

Online estimation and adaptive control of penicillin fermentation

The paper describes an investigation into the application of state estimation and adaptive control to fed-batch fermentation for penicillin production. The work forms part of an industrial collaborative project, the aim of which is the optimising control of large fed-batch fermenters. Estimates of biomass are made using an extended Kalman filter from on-line measurements of carbon dioxide production rate and fermentation volume. The estimated biomass is controlled to a reference trajectory by an adaptive generalised predictive controller manipulating the sugar feed rate. A comparison of performance is made with control by conventional proportional plus integral (PI) techniques. The results presented are obtained from simulation studies while validation studies are carried out on both a 30 1 pilot plant fermenter and the industrial plant.

Fuzzy Control Application to Glutamic Acid Fermentation

Consumption rate of ammonia in glutamic acid fermentation was found to be correlated with consumption rate of sugar. This gives a good control strategy for sugar feed rate to keep sugar concentration in a suitable range in fed-batch culture of glutamic acid fermentation.Slight changes of culture conditions, however, make some troubles in this control scheme. Fuzzy theory application could be found to be effective in such cases.

Microbial aspects of fermentation process development

AbstractAspects of fermentation dynamics are discussed, especially from the point of view of process development. Initial examples are from laboratory work in continuous culture. After this the economic and dynamic aspects of protein production by continuous culture are reviewed. In the last part the optimisation of the pencillin fermentation is considered, based on the use of a model which predicts yields, with a fermentation limited by the rate of oxygen transfer to the culture, when penicillin production falls at low growth‐rates. A process involving a sugar feed is considered, the main factors being the concentration of nitrogen in the medium, which governs initial cell production, and sugar feed rate which maintains further growth. The model predicts high yields over a wide variety of conditions. This indicates the difficulty of a pilot‐plant optimisation programme, when the maximum yield point is not critical. Other factors in the fermentation are also discussed.