Modeling and simulation of lactic acid fermentation with inhibition effects of lactic acid and glucose

An unstructured mathematical model for lactic acid fermentation was developed. This model was able to predict the inhibition effects of lactic acid and glucose and was confirmed to be valid with various initial concentrations of lactic acid and glucose. Simulation of energy production was made using this mathematical model, and the relationship between the kinetics of energy metabolism and lactic acid production was also analyzed.     

The effects of allatectomy and juvenile hormone replacement on the development of host-seeking behaviour and lactic acid receptor sensitivity in the mosquito Aedes aegypti

Host-seeking behaviour in newly emerged Aedes aegypti (L.) females is not expressed immediately after adult eclosion but develops gradually over a period of approximately 3-4 days. This development is accompanied by an apparent maturation of the antennal chemosensory afferent neurons involved in the detection of the airborne host attractant lactic acid. Since these events coincide in time with juvenile hormone-dependent previtellogenic ovarian growth and since the expression of other reproduction-associated behaviour has previously been shown to be dependent on juvenile hormone, the effects of juvenile hormone removal and replacement on the development of host-seeking behaviour and the response characteristics of the lactic acid-sensitive receptors were investigated. No effect of juvenile hormone removal by allatectomy or juvenile hormone replacement or augmentation by topical application of the juvenile hormone mimic methoprene was found. It was concluded that this hormone is not involved in the appearance of host-seeking behaviour or the apparent maturation of the lactic acid receptors that occurs during early imaginal life.     

Product inhibition in simultaneous saccharification and fermentation of cellulose into lactic acid

The product, lactic acid, strongly inhibited microbial activity in lactic acid fermentation. The volumetric productivity declined from 1.19 g/l.h with zero lactic acid (control) to only 0.18 g/l.h when lactic acid reached 65 g/l. Lactic acid also inhibited cellulase activity but less severely than the inhibition on microbial activity as lactic acid above 90 g/l was needed for 50% inhibition. A gradual deterioration of the Simultaneous Saccharification and Fermentation (SSF) process occurred with the build-up of lactic acid and the rate-controlling step in SSF shifted from hydrolysis to fermentation as the bioprocess proceeded.     

Mechanisms of lactic acid gustatory attraction in Drosophila

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The challenge of invasive mosquito vectors in the U.K. during 2016–2018: a summary of the surveillance and control of Aedes albopictus

Mosquito‐borne diseases resulting from the expansion of two key vectors, Aedes aegypti and Aedes albopictus (Diptera: Culicidae), continue to challenge whole regions and continents around the globe. In recent years there have been human cases of disease associated with Chikungunya, dengue and Zika viruses. In Europe, the expansion of Ae. albopictus has resulted in local transmission of Chikungunya and dengue viruses. This paper considers the risk that Ae. aegypti and Ae. albopictus represent for the U.K. and details the results of mosquito surveillance activities. Surveillance was conducted at 34 points of entry, 12 sites serving vehicular traffic and two sites of used tyre importers. The most common native mosquito recorded was Culex pipiens s.l. (Diptera: Culicidae). The invasive mosquito Ae. albopictus was detected on three occasions in southern England (September 2016, July 2017 and July 2018) and subsequent control strategies were conducted. These latest surveillance results demonstrate ongoing incursions of Ae. albopictus into the U.K. via ground vehicular traffic, which can be expected to continue and increase as populations in nearby countries expand, particularly in France, which is the main source of ex‐continental traffic.     

State‐wide survey of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in Florida

Aedes aegypti and Aedes albopictus are invasive mosquito species with geographic ranges that have oscillated within Florida since their presence was first documented. Local transmission of dengue, chikungunya, and Zika viruses serves as evidence of the public health importance of these two species. It is important to have detailed knowledge of their distribution to aid in mosquito control efforts and understand the risk of arbovirus transmission to humans. Through a partnership involving the University of Florida Institute of Food and Agricultural Sciences Cooperative Extension Service and the Florida Medical Entomology Laboratory; the Florida Department of Health; and mosquito control agencies throughout Florida, a container mosquito surveillance program involving all life stages was launched in the summer of 2016 to detect the presence of Ae. aegypti and Ae. albopictus. Results from this survey were mapped to provide a picture of the current known distribution of Ae. aegypti and Ae. albopictus in Florida. Aedes aegypti and/or Ae. albopictus were detected in the 56 counties that were part of the survey. Only Aedes albopictus was detected in 26 counties, primarily in the panhandle region of Florida. The results of this work underscore the importance of maintaining container mosquito surveillance in a state where chikungunya, dengue, and Zika viruses are present and where there is continued risk for exotic arbovirus introductions.     

The community ecology of Aedes egg hatching: implications for a mosquito invasion

Abstract. 1. A recently introduced treehole mosquito from Asia, Aedes albopictus , is spreading throughout eastern North America, especially in tyre-refuse piles. Previous studies have identified inhibitory effects of larvae on egg hatch as a potential population regulatory mechanism within Aedes. Larva-egg interactions may also occur between species. This experiment assesses the ability of larvae of A. albopictus and two possible competitors in North America, A.triseriatus and A.aegypti , to suppress hatching of conspecific and congeneric eggs.
2. We exposed eggs of each species to varying combinations of larval species and density for 24h and assessed subsequent hatch rates. Aedes albopictus eggs exhibited the lowest level of inhibition when exposed to high larval densities; moreover, at the lowest larval density they imposed the most intense interspecific hatch inhibition.
3. Discretionary hatching in response to larval density may influence community composition by promoting the spread of A.albopictus , perhaps even leading to its dominance within North American Aedes communities.     

Mosquitoes of Rarotonga,Cook Islands: A survey of breeding sites

Abstract

Two surveys of Rarotonga, Cook Islands (21°20^'S, 160°16^'W) were made to determine the mosquito fauna of the island, and to identify the habitats required for breeding by searching for larvae. The first survey was made during the “dry season” in May 2001, the second during the “wet season” in February 2002. The mosquito fauna comprised four species Culex (Culex) quinquefasciatus Say, Culex (Culex) annulirostris Skuse, Aedes (Stego‐myia) aegypti (Linnaeus) and Aedes (Stegomyia) polynesiensis Marks. Larvae of the Culex species were most often found in larger natural and artificial water bodies. The Aedes species bred in both natural and artificial containers of all sizes. Ae. polynesiensis was the most widespread species, using natural holes in all regions as well as artificial containers in the urban areas. Most larvae of Ae. aegypti were located in small artificial containers. The two Aedes species are the vectors of dengue fever on the island. Mosquito control during outbreaks should specifically target the artificial containers preferred by Aedes sp. for breeding habitats.     

Oviposition by Aedes aegypti and Aedes albopictus: Influence of congeners and of oviposition site characteristics

We investigated the oviposition behavior of Ae. aegypti and Ae. albopictus. In particular we examined whether small‐scale site characteristics and the presence of conspecifics or congeners altered oviposition by these mosquitoes. Various combinations of females of the two species were allowed to oviposit inside cages among either vegetation (potted plants) or structural components (wood and concrete blocks). Numbers of eggs deposited per female were compared between species, sides, and treatments. Most significant differences between treatments and species involved differences between single species and mixed species treatments. Ae. aegypti deposited more eggs/female in the vegetation side than in the structure side whereas the opposite pattern was evident for Ae. albopictus. Ae. aegypti females had higher frequency of skip oviposition than Ae. albopictus. An average of 63% of the containers in the two‐species treatments contained eggs of both species, with more frequent joint occurrences observed in the treatment with three females of each species than in the treatments with one of each. Our results point to the existence of various interactions between gravid Ae. aegypti and Ae. albopictus females at or near the oviposition sites but further experimental work is necessary to fully characterize the interactions and their specific mechanisms.     

Direct lactic acid fermentation: Focus on simultaneous saccharification and lactic acid production

In the recent decades biotechnological production of lactic acid has gained a prime position in the industries as it is cost effective and eco-friendly. Lactic acid is a versatile chemical having a wide range of applications in food, pharmaceutical, leather and textile industries and as chemical feedstock for so many other chemicals. It also functions as the monomer for the biodegradable plastic. Biotechnological production is advantageous over chemical synthesis in that we can utilize cheap raw materials such as agro-industrial byproducts and can selectively produce the stereo isomers in an economic way. Simultaneous saccharification and fermentation can replace the classical double step fermentation by the saccharification of starchy or cellulosic biomass and conversion to lactic acid concurrently by adding inoculum along with the substrate degrading enzymes. It not only reduces the cost of production by avoiding high energy consuming biomass saccharification, but also provides the higher productivity than the single step conversion by the providing adequate sugar release.     

几种驱避化合物对白纹伊蚊寄主搜寻能力的影响

研究了白纹伊蚊Aedes albopictus在含不同浓度的驱避化合物的空间内停留不同时间后,对其寄主搜寻能力的影响。结果显示：在密闭空间中, 分别以0.013～0.500 μg/cm³浓度的柠檬醛、丁香酚、芳樟醇、香叶醇、茴香醛处理白纹伊蚊24～96 h后,试蚊均出现不同程度的定向寄主抑制,其中以茴香醛及香叶醇抑制效果最佳,但香茅醛各处理组试蚊均未受到影响。白纹伊蚊搜寻定向寄主能力受到抑制的个体,在实验室正常饲养后,可逐渐恢复;但茴香醛0.250 μg/cm³处理试虫96 h后,一直未能恢复正常的吸血行为。研究结果提示,茴香醛与香叶醇作为优良的空间驱避剂,在白纹伊蚊防控技术领域可发挥重要作用。     

On-line estimation of biological variables during pH controlled lactic acid fermentations

Indirect measurement of lactose, galactose, lactic acid, and biomass concentration from on-line sodium hydroxide weight measurements have been obtained for pure and mixed batch cultures of Streptococcus salivarius ssp. thermophilus 404 and Lactobacillus delbrueckii subsp. bulgaricus 398 conducted at controlled pH and temperature. Linear correlations were established between the equivalent sodium hydroxide concentration and the lactose (substrate), galactose and lactic acid (products) concentrations while nonlinear relationships were developed between biomass and lactic acid concentrations. These nonlinear relationships took into account the inhibitory effect of lactic acid on growth and acidification. The indirect measurements of biomass concentration were introduced into a nonlinear estimator of the state variables and of the specific growth and lactic acid production rates. Good agreement was found between estimated and measured biomass concentrations (error index ranging from 10.8% to 12.6%). The results showed the feasibility of on-line estimation of biomass concentration and of the specific kinetics from NaOH addition weight measurements and its applicability for monitoring lactic acid fermentations. Using off-line measurements of L(+) and D(-) lactic acid concentrations, the evolution of the concentration of each strain in mixed cultures was obtained from the relationships proposed for the mixed cultures. (c) 1994 John Wiley & Sons, Inc.     

抗灰葡萄孢霉菌乳酸菌的筛选

从80株乳酸菌中筛选出45株具有抗灰葡萄孢霉菌活性的乳酸菌菌株,其中10株具有较强抗灰葡萄孢霉菌活性。对这10株乳酸菌菌株的抗植物致病真菌谱进行了研究,这10株乳酸菌对番茄早疫病菌,甜瓜疫霉菌,甜瓜枯萎病菌,苹果炭疽病菌的生长均有较强的抑制作用。其中1株具有广谱抗植物致病真菌活性的乳酸菌菌株BX6-4为植物乳杆菌。经番茄离体叶片接种试验发现,植物乳杆菌BX6-4的发酵液能够在体外强烈地抑制灰葡萄孢霉菌的生长。     

Extractive lactic acid fermentation using ion-exchange resin

Lactic acid fermentation is an end-product-inhibited reaction. The restriction imposed by lactic acid on its fermentation can be avoided by extractive fermentation techniques. Studies were performed by attaching an ion-exchange resin packed column with a 2-L fermentor for separation of lactic acid. The fermentation, in a conventional batch mode, resulted in a lactic acid yield of 0.828 g . g(-1) and a lactic acid productivity of 0.313 g . L(-1) . h(-1). However, these could be further enhanced to 0.929 g . g(-1) and 1.665 g . L(-1) . h(-1) by extractive fermentation techniques. The effect of temperature on extractive fermentation was remarkable and has been included in this work.     

生物基乳酸生物转化研究进展

乳酸的发酵生产技术已取得了长足的进步,作为一种重要生物基化学品,乳酸除了可用于食品工业及生产聚乳酸外,亦可作为一种重要的平台化合物,用于生产丙烯酸、丙酮酸、1,2-丙二醇、乳酸酯等。文中重点综述了以生物基乳酸为原料经脱水、脱氢、还原及酯化反应生产乳酸衍生物的生物转化工艺,对该领域的发展趋势进行了展望。     

Laboratory evaluation of lactic acid on attraction of Culex spp. (Diptera: Culicidae)

The role of lactic acid was evaluated for attraction of Culex nigripalpus, Culex quinquefasciatus, Culex tarsalis, and Aedes aegypti in the laboratory using a dual‐port olfactometer. When lactic acid was combined with chicken odor, attraction was increased for Cx. quinquefasciatus compared to chicken odor alone but not for Cx. nigripalpus, Cx. tarsalis, and Ae. aegypti. Lactic acid combined with hand odor did not change attraction of Cx. tarsalis and Ae. aegypti but decreased attraction of Cx. nigripalpus and Cx. quinquefasciatus. The addition of lactic acid to CO₂ increased attraction of Ae. aegypti and Cx. quinquefasciatus but reduced attraction of Cx. nigripalpus and Cx. tarsalis. Use of commercial lactic acid baits with CO₂ resulted in a similar trend except for Cx. nigripalpus which showed no difference. A blend of lactic acid, acetone, and dimethyl disulfide was attractive to Ae. aegypti (63.4%) but elicited low responses by all Culex spp. (1.3–26.8%). Addition of the blend to CO₂ increased attraction of Ae. aegypti and Cx. quinquefasciatus but reduced attraction of Cx. nigripalpus and Cx. tarsalis. The mixture of compounds plus CO₂ was as attractive as a hand for Cx. quinquefasciatus, Cx. tarsalis, and Ae. aegypti.     

Batch and fed-batch fermentation of optically pure D (-) lactic acid from Kodo millet (Paspalum scrobiculatum) bran residue hydrolysate: growth and inhibition kinetic modeling

Abstract

A low-cost Kodo millet bran residue was utilized as feedstock for the production of D (?) lactic acid (DLA) using Lactobacillus delbrueckii NBRC3202 under anaerobic condition. Data culled from a series of batch fermentation processes with different initial Kodo millet bran residue hydrolysate (KMBRH) and DLA concentrations were used for kinetic model development. Both simulated and experimental data were in good agreement for cell growth, KMBRH utilization, and DLA formation. The values of kinetic constants specific growth rate, (μ_m = 0.17?h^?1); growth (α_P = 0.96?g.g^?1) and non-growth (β_P = 1.19?g.g^?1.h^?1) associated constant for DLA production and the maximum specific KMBRH utilization rate, (q_{G, max} = 1.18?g.g^?1.h^?1) were in good agreement with the literature reports. Kinetic analysis elucidated that L. delbrueckii growth was predominantly influenced by KMBRH limitation and highly sensitive to DLA inhibition. Fed-batch fermentation studies demonstrated the existence of substrate and product inhibition paving the scope for process intensification.     

Evaluation of lactic acid bacteria autolysate for the supplementation of lactic acid bacteria fermentation

At the end of culture in a carbon-limited medium, i.e. the best conditions for subsequent autolysis, lactic acid bacteria were harvested and autolysed at 50 °C for 24 h. The resulting supernatant was then successfully tested as a substitute for industrial yeast extract for the supplementation of whey permeate and its conversion into lactic acid: for almost equivalent total nitrogen amounts of both supplements, the same growth and production rates were recorded.     

Egg hatching inhibition: field evidence for population regulation in a treehole mosquito

ABSTRACT. 1. We investigated the influence of larval density on egg hatching in the treehole mosquito, Aedes triseriatus Say (Diptera: Culicidae) by submerging laboratory-produced egg batches in natural habitats stocked with fixed densities of larvae.
2. We found a significant decrease in hatching rate as larval density increased. The results suggest that inhibited eggs refrain from hatching into environments in which competitive effects of large larvae are potentially severe, and in which cannibalism may occur.
3. The amount of time the egg batches were exposed to experimental conditions (between 2 and 16 days) had no significant influence on hatch rate.     

Multiple activities of insect repellents on odorant receptors in mosquitoes

Several lines of evidence suggest that insect repellent molecules reduce mosquito-host contacts by interacting with odorants and odorant receptors (ORs), thereby ultimately affecting olfactory-driven behaviours. We describe the molecular effects of 10 insect repellents and a pyrethroid insecticide with known repellent activity on two highly specific Aedes aegypti (Diptera: Culicidae) ORs, AaOR2 + AaOR7 and AaOR8 + AaOR7, exquisitely sensitive to key mosquito attractants indole and (R)-(-)-1-octen-3-ol, expressed in oocytes of Xenopus (Anura: Pipidae). Our study demonstrates that insect repellents can both inhibit odorant-evoked currents mediated by ORs and independently elicit currents in the absence of odorants. All of the repellents had effects on one or both ORs; most of these compounds were selective inhibitors and showed a high degree of specificity in their capacity to activate the two ORs. These results show that a range of insect repellents belonging to structurally diverse chemical classes modulate the function of mosquito ORs through multiple molecular mechanisms.