Purification and properties of elm mottle virus

A virus obtained commonly from Wych elm (Ulmus glabra) in Scotland showing ringspot and line-pattern leaf symptoms was serologically related to elm mottle virus (EMotV) from East Germany. The virus was seed-borne in elm and was transmitted by inoculation of sap to elm and twenty-one herbaceous species. No symptoms developed in infected elm seedlings kept in the glasshouse. In Chenopodium quinoa sap, EMotV lost infectivity after diluting to 10^-4, after 10 min at 60 ^oC, or 9 days at 18 ^oC. When purified from C. quinoa sap by clarification with n-butanol (8-5 %, v/v) and differential centrifugation, preparations contained quasi-spherical particles mostly 26–29 nm m diameter (mean = 28 nm) which sedimented as three nucleo-protein components with sedimentation coefficients (s^o₂o, w) of 83, 88 and 1 or S; most infectivity was associated with the 101 S component but infectivity was enhanced by adding the slower sedimenting components. When centrifuged to equilibrium in caesium chloride solution at 4 ^oC, purified virus preparations were largely degraded and contained many non-infective particles c. 15–22 nm in diameter, and intact infective particles which formed a band of density c. 1–34 g/cm³. Polyacrylamide gel electrophoresis indicated that EMotV contained a single major protein species of estimated mol. wt. 25000 and five RNA species of estimated mol. wt. 1–30, 1.15, 0–82, 0 39 and 0–30 times10⁶. Gel electrophoresis of RNA extracted from the separated components indicated that the 101 S component contained 1–30 x io⁶ mol. wt. RNA and the 83 S component 0–82 times 10⁶ mol. wt. RNA. In these and other properties, EMotV resembles the serologically unrelated tobacco streak virus.     

The occurrence, hosts and properties of lilac chlorotic leafspot virus, a newly recognised virus from Syringa vulgaris

Lilac chlorotic leafspot virus (LCLV), a hitherto undescribed virus, was isolated from three of 65 lilacs (Syringa vulgaris) with chlorotic leafspotting symptoms growing in S.E. England. The virus was transmitted readily by sap-inoculation to 21 of 52 species from eight of 20 families, but it was not seed-borne in four hosts or transmitted in the semi-persistent manner by any of four aphid species. The virus was moderately stable in vitro; sap from Chenopodium quinoa was infective after 10 min at 60 but not 65 ^oC, after 8–16 days at 20 ^oC or 25–30 wk at 2 ^oC, and after dilution to 10^-3 but not 10^-4. Up to 180 mg of purified virus per kg leaf tissue were obtained from C. quinoa by clarification of buffered leaf extracts with 8% (v/v) n-butanol, followed by one cycle of differential centrifugation and molecular permeation chromatography on controlled pore glass beads (700 Å, 120–200 mesh). LCLV has fragile flexuous filamentous particles which, when intact, mostly measured c. 12-5 times 1500–1600 nm; the helical substructure (pitch c. 3–7 nm) was clearly visible on some particles mounted in uranyl acetate. The particles sedimented as a single component (sedimentation coefficient 96 S; buoyant density 1–302 g cm^-3) and contained c. 5% nucleic acid and a single polypeptide of mol. wt 27 times 10³. Although these properties place LCLV in the closterovirus group, the virus showed no serological relationship to any of six closteroviruses (beet yellows, beet yellow stunt, carnation necrotic fleck, apple chlorotic leafspot, apple stem grooving and potato virus T) and differed from other recognised or possible members of this group in host range and/or symptoms induced in indicator species. The infrequent occurrence of LCLV in lilac in S.E. England indicates that the virus could probably be eradicated by selecting only virus-free plant material for propagation.     

Aerated-steam treatment for control of Alter nana tenuis on lobelia seed

Alternaria tenuis may cause severe seedling blight, damping-off and leaf spotting of the bedding plant lobelia. Disease transmission from seed naturally and artificially infected by A. tenuis was demonstrated and the pathogenicity of four isolates established. Soaking of lobelia seed in 0–2% thiram suspension at 30 ^oC for 12 h adversely affected the rate of germination and did not consistently reduce infection to acceptable levels. Treatment with aerated steam at 50–51 ^oC for 15–20 min reduced seed infection to undetectable or insignificant levels and caused only slight damage to the seed. In glasshouse trials seed treated with aerated steam performed significantly better than seed soaked in thiram suspension both in terms of germination and foliage production.     

The effect of temperature on viability of imbibed weed seeds

Imbibed seed of 10 common arable weeds were placed in trays in initially moist soil and, after imbibing for 2h, heated in ovens/incubators set to 31^oC, 42^oC, 56^oC, 75^oC or 100^oC for 0.5, 1, 2, 4, 8 or 16 days or at 102^oC, 155^oC, 204^oC or 262^oC for 0.5, 1, 2, 5, 7.5 or 10 min. After heating, seeds were incubated for 28 days at 10/20^oC or 20/30^oC on a 12 h dark/light regime, depending on species, and germination recorded. At the lower temperatures, germination of all species was prevented by temperatures of 75^oC or higher for periods of 0.5 days or more. Germination was lower after treatment at 56^oC than at 31^oC or 42^oC for all species except Rumex obtusifolius. The maximum temperature required to prevent germination varied among species and was of greater importance than the duration of heating. Germination was variable with duration of heating. At the higher temperatures, there was very little germination of any species after heating at 204^oC for 7.5 min or 262^oC for 5 min or more. Seeds were greatly buffered from the air temperature by 3 mm of soil, throughout the shorter duration of heating. The average temperature of the soil, over the 10 min heating required to prevent over 90% germination, varied among species and ranged from 48^oC for Avena fatua to 65^oC for R. obtusifolius. This work implies that composting systems maintained at 65^oC are unlikely to provide an efficient method of weed control. Recommendations for improvement of the laboratory technique are suggested.     

Hirsutella thompsonii, a fungal pathogen of mites. I. Biology of the fungus in vitro

Hirsutella thompsonii, a moniliaceous fungus pathogenic to mites, grew and sporulated on sterilised wheat bran. The effects of environmental factors were studied on the fungus grown on potato-dextrose-agar (PDA). The fungus was mesothermophilic. Growth, sporulation and conidial germination were best at 25^o-30 ^oC. Conidia kept at 37 ^oC for 5 days on PDA died, but those held at 5 ^oC germinated upon a subsequent removal to 25 ^oC. Almost all conidial germ tubes survived an 8 h exposure to 3–5% r.h. and to 60% r.h., but subsequently the former grew poorly at 100% r.h. H. thompsonii sporulated equally well in continuous darkness or light, and produced typical chlorinous to light olive-green mycelium and conidia under all conditions. A 2 h exposure of naked mycelium and conidia (which have melanised walls) to u.v. irradiation failed to kill the fungus.     

Investigations of carnation viruses

Carnation vein mottle virus (CarVMV) is rare in glasshouse carnations in Britain, although locally common in Dianthus barbatus in private gardens. In Sim carnations free from other viruses, CarVMV caused slight diffuse chlorotic mottling in the younger leaves, decreased flower yield by c. 22%, and caused flower breaking in cvs William Sim and Dusty. In non-Sim cultivars Pink Shibiuya, Orchid Beauty and Vesta, leaf symptoms and flower breaking were more pronounced. In mixed infections with carnation mottle virus, symptoms were much more severe. CarVMV was not eliminated from carnation or D. barbatus plants grown for 4 wk at 37^oC, and only rarely from cuttings then taken from them, but it was readily eliminated by meristem-tip culture. Myzus persicae adults or nymphs acquired and transmitted the virus within a total time of 4 min, and remained infective for 30–60 min if feeding, or for 75 min if starved. The carnation aphid, M. persicae f. dianthi, transmitted the virus much less efficiently. The virus was not transmitted by dodder (Cuscuta campestris), or through seed of D. barbatus or Chenopodium quinoa. The maximum infective dilution in sap of D. barbatus, carnation and C. quinoa ranged from 10^-2 to 10^-5. The virus withstood 10 min at 60 but not 65^oC, up to 9 days at c. 18^oC or 3–4 wk at c. 2^oC. CarVMV infected twenty-two of 107 plant species in six of thirty-seven families; suscepts were confined to the Chenopodiaceae, Caryophyllaceae and closely allied families. C. quinoa was the best local lesion assay host. Seedling clones of D. barbatus, selected as resistant to carnation mottle virus, proved the best indicator and propagation species. Up to 50 mg virus/kg tissue were obtained by butanol clarification followed by differential and density gradient centrifugation. The preparations contained a single sedimenting component, s_20w= 144S, and had flexuous filamentous particles, c. 790 times 12 run; the particles contained a single polypeptide, mol. wt 34800, and 5% of a single-stranded ribonucleic acid (RNA) with nucleotide base ratios of G21: A25: C25: U29. Serologically CarVMV was related distantly to turnip mosaic (cabbage black ring strain), pea mosaic, watermelon mosaic (Strain 2) and bean yellow mosaic viruses, more closely to pepper veinal mottle virus, but unrelated to twelve other potyviruses. CarVMV is not at present a danger to carnation crops in Britain, but the recent trend of sending carnation plants to overwinter outdoors in warmer countries involves potential risks of more rapid spread by effective vector races of M. persicae.     

Pepper veinal mottle virus-a new member of the potato virus Y group from peppers (Capsicum annuum L. and C. frutescens L.) in Ghana

Pepper veinal mottle virus (PVMV), a previously undescribed virus widespread in Capsicum annuum and C. frutescens in the Eastern Region of Ghana, is acquired and inoculated in 2 min feeding periods by aphids (Myzus persicae and Aphis gossypii); it is transmissible by inoculation of sap to eleven of fifteen Solanaceae and to five of forty-six other species within three of seventeen other families. The virus was propagated in Nicotiana clevelandii and Petunia hybrida, and assayed in Chenopodium quinoa, C. amaranticolor and C. murale. Sap from Capsicum annuum was infective after dilution to 10^-3 but not 10^-4, after 10 min at 55 but not 60^oC, and after 7 but not 8 days at 25^oC. Lyophilized sap from P. hybrida was infective after 6 years in vacuo. Yields of 10–25 mg of virus per kg of leaf tissue were consistently obtained from P. hybrida or N. clevelandii by extracting systemically infected leaves in 0.5 M borate (pH 7.8) containing 0.2% mercaptoethanol and chloroform, followed by repeated precipitation with 50 g polyethylene glycol (M.W. 6000) per l, several cycles of differential centrifugation and centrifugation in sucrose density-gradient columns. Virus preparations had ultraviolet absorption spectra typical of a nucleoprotein containing c. 6% nuclei acid (A 260/280 = 1.25; A 260/246 = 1.27) and contained numerous unaggregated and unbroken filamentous particles c. 770 times 12 nm which sedimented as a single component with a sedimentation coefficient (s^o_20,w) of 155 S. PVMV contained RNA (moles %: G = 24, A = 23, C = 27, U = 26), and a single protein species with a molecular weight of 32000–33000 daltons. PVMV was not serologically related to potato virus Y (three strains), or to twelve other morphologically similar viruses, and seems to be a distinct member of the potato virus Y group. The cryptogram of PVMV is R/(I):*/(6):E/E:S/Ap.     

Response of squash to ethylene and chilling

Freshly harvested but already cured Acorn squash (Cucurbita pepo cv. Acorn) were stored for 4 wk in storage environments of 20, 15, 10 , 5 and o ^oC, with or without 5 μl 1-1^-1 ethylene. Ethylene had no significant effect on overall acceptability, weight loss, dry matter, and ion leakage, but did enhance respiration at 15 and 20 ^oC. Temperature had a significant effect on weight loss, dry matter and overall acceptability. Squash stored at 15 and 20 ^oC had better flavour and texture than those stored at 0–10 ^oC, when cooked. Quality attributes such as flavour and texture may be more useful than physiological parameters in detecting insipient chilling injury in squash.     

Early warning of egg hatching in pea moth (Cydia nigricana)

Female pea moths (Cydia nigricana) kept at 23 ^oC began to lay eggs 2–3 days after emergence, lived for 16–21 days and laid on average 71 eggs. Individuals kept in field cages lived for slightly longer and laid on average 91 eggs. About 85% of eggs were laid during the first 11 days of the oviposition period, usually in the late afternoon and early evening. The relationship between the rate of egg development and temperature was defined. The estimated developmental zero was 9-4 ^oC at constant temperatures and 8-5 ^oC at fluctuating temperatures. Above 28 ^oC mortality increased and above 31 ^oC development was apparently retarded. Development at constant temperatures took 6–16% longer than at fluctuating temperatures with the same mean. Estimates of hatching dates in the field made from temperature data recorded at several sites in and near a pea crop, and 8 km distant, were usually within a day of the observed date. In warm weather, estimated and observed dates usually coincided; in cooler weather hatching was 2–3 days later than expected. Hatching dates predicted from temperature data after only 80% of development had occurred were correct on 28 out of 36 occasions. An example is given to show how the method could be used eventually with a sex attractant trapping system to provide early warning of first hatching and spraying dates.     

The influence of temperature on the susceptibility of vine weevil, Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae), larvae to Metarhizium anisopliae (Deuteromycotina: Hyphomycetes)

Mortality of Otiorhynchus sulcatus (Fabricius) larvae at 10^oC, 15^oC, 20^oC and 25^oC following treatment with 10⁷conidia ml“¹suspensions of six Metarhizium anisopliae (Metschnikoff) Sorokin isolates was temperature dependent. In all cases, the LT₅₀s were inversely related to temperature, but the nature of this response varied between isolates. Strain 101-82 was the most virulent isolate at 25^oC with an LT₅₀ of 3.7 days, but it was the least virulent isolate at 15^oC and it failed to kill any O. sulcatus larvae at 10^oC. In contrast, strain 159-83 had the lowest virulence at both 20^oC and 25^oC, whereas it was the most virulent isolate at 10^oC with an LT₅₀ of 20.0 days. The mortality rates followed a similar pattern and were positively related to temperature in all cases with the exception of strain 159-83 at 25^oC. Mycosis development was examined on larvae treated with strain 275-86 and significant differences were obtained between all four temperatures. Sporulation commenced after approximately 2.75 days at 25^oC, but took nearly 11 days at 10^oC. The infection rates also varied between temperatures; sporulation occurred on 98% of the treated larvae at 25^oC, but only on 93%, 87% and 49% of the larvae at 20^oC, 15^oC and 10^oC, respectively. The results of these bioassays demonstrate that temperature has a significant effect on the virulence of M. anisopliae. The differences between fungal strains also emphasises the importance of selecting isolates for specific situations on the basis of their temperature profiles.     

Some hosts and properties of narcissus latent virus, a carlavirus commonly infecting narcissus and bulbous iris

Narcissus latent virus (NLV) is common in many cultivars of narcissus and bulbous iris, but was detected in only one of nineteen cultivars of nerine. It induced symptoms in some narcissus cultivars, but inconspicuous infection in bulbous iris and nerine. NLV was not seed-borne in narcissus or Nicotiana clevelandii but was transmitted readily by aphids (Acyrthosiphon pisum, Aphis gossypii and Myzus persicae) in the non-persistent manner and by sap-inoculation to twelve of fifty-three species from three of sixteen families. Sap from N. clevelandii was infective after dilution to io^-3 but not io*, after 10 min at 65 but not 70 ^oC or after 3–4 days at 20 ^oC or 16–32 days at 2 ^oC. Purified virus preparations were obtained from infected N. clevelandii by clarification of buffered leaf extracts with diethyl ether and carbon tetrachloride, followed by one or two cycles of differential centrifugation and molecular permeation chromatography. NLV has filamentous particles c. i3times65onm which sediment as a single component (i^o_{20, w}= 156S). They contain c. 5% nucleic acid and a single polypeptide of mol. wt 32·6 × 10³. The biological and physical properties of NLV place it in the carlavirus group; it is serologically related to lily symptomless virus, but not to fourteen other authentic carlaviruses. NLV has the cryptogram */*:*/(5):E/E:S/Ve/Ap.     

The effects of different blend ratios and temperature on the active space of the Oriental fruit moth sex pheromone

Abstract The wing-fanning activation response of male Oriental fruit moths (OFM), Grapholita molesta (Busck), in the field to the three-component pheromone containing the female-produced ratio of components (Z8-12:OAc + 6% E8-12:OAc + 3% Z8-12:OH) was compared with the response to blends containing 2,10 and 20% E with 3% OH, and the 6% E blend containing 30 and 100% OH. Comparisons were made over three temperature ranges: 15–17, 20–21 and 26–28^oC. Both the maximum response distance and male response specificity were significantly altered by changes in odour quality as well as temperature. For blends containing different Z/E ratios the maximum response distance increased significantly with temperature. Response specificity was most pronounced at the 20–21^oC range, with males displaying a lower threshold for the natural 6% E ratio, evidenced by the fact that fewer males responded and at closer distances to the source with off-ratios. At 26–28^oC response specificity for the Z/E ratios was much reduced, primarily due to more males activating to off-ratios. With blends containing different proportions of Z8-12:OH in the 6% E blend, increasing temperature increased the maximum response distance for all treatments, but in addition increasing the proportion of OH alone from 3% to 30% significantly increased the maximum response distance over the three temperature ranges tested. This increase occurred without affecting the proportion of responders or the distribution of response distances around the mean value. However, with 100% OH added to the blend, whereas male response was high at 20–21^oC, the distribution of response distances was significantly more variable than with 3% or 30%, and male response was eliminated or very low at 15–17^oC and 26–28^oC. Our results support previous studies showing that peak response levels in this species are dependent on male perception of the natural blend of components, and that males have a high degree of specificity for the qualitative properties of the pheromone. However, the present results also extend those of previous flight tunnel tests in which response specificity was most pronounced in the upwind flight phase of the sequence, by showing that male OFM also display a     

Single-cell protein of Rhodotorula sp. Y-38 from ethanol, acetic acid and acetaldehyde

Summary Continuous cultivation of Rhodotorula sp. Y-38 was carried out on ethanol, acetic acid or acetaldehyde. At a feed concentration of 1.0 % (w/v) ethanol, the cell yield of 64 g/100 g ethanol and crude protein of 52 g/100 g biomass were obtained at D=0.5 h^-1. The respective value of the content of amino acids and nucleic acids was 42.6 and 9.4 g/100 g biomass. At 2.0 % (w/v) acetic acid, cell yield was found to be 50 g/100 g acetic acid at D=0.4 h^-1. The optimum dilution rate ranged between 0.3 and 0.4 h^-1. At 0.05 % (w/v) acetaldehyde, the maximum cell yield was obtained at D=0.14 h^-1.     

Light-induced changes in extracellular calcium concentration in the compound eye of Calliphora,Locusta and Apis

Summary Ion-selective microelectrodes inserted into the compound eyes of Calliphora, Locusta and Apis were used to monitor the changes in extracellular concentration of Ca²⁺ (Ca_o) brought about by a 1-min exposure to white light (maximal luminous intensity ca. 10³ cd/m²).In the blowfly retina such stimulation causes a decrease in Ca_o. At high light intensities the Ca_o signal is phasic, falling over about 6 s to a transient light-induced minimum (Ca_o= -6.2% ± 0.4%, n = 20, SE) and then rising to an approximately stable plateau (-3.3% ± 0.6%). In migratory locusts the light-induced minimum corresponds to a Ca_o of -13.8% ± 1.6% (n = 10), and at the plateau the Ca_o decrease is-13.2% ± 1.5%. In honey-bees Ca_o at first decreases only slightly, by -2.6% ± 1.0% (n = 10); by the end of the 1-min stimulus the extracellular concentration averages 33.6% ± 14.6% above the dark level.The results suggest a relationship between the position of the characteristic curve of the photoreceptor in the dark-adapted state, the occurrence of quantum bumps, and light-induced increases or decreases in Ca_o. Therefore the species differences might be interpreted as a consequence of differences in the intracellular dark concentration of Ca²⁺.Abbreviations Ca_i intracellular Ca²⁺ concentration - Ca_o extracellular Ca²⁺ concentration     

Short communication: Thermostability of α-amylase produced by Bacillus sp. E2—a thermophilic mutant

An -amylase from a hyper-producing strain of Bacillus (sp. E2) was stable at 70°C for 30 min but was quickly inactivated at higher temperatures. In the presence of 10mm Ca²⁺ and starch (20% w/v), however, the enzyme was stable at 90°C for 10 min and after 30 min at 100°C still retained 26% of its initial activity.     

Responses of the tropical bont tick, Amblyomma variegatum (Fabricius), to its aggregation-attachment pheromone presented in an air stream on a servosphere

Male Amblyomma variegatum ticks feeding on a host release a mixture of o -nitrophenol and methyl salicylate which serves to attract conspecifics. The behavioural responses of A. variegatum on a servosphere to these volatiles presented in an air stream are detailed here. In still air, ticks walked on all eight legs, but with long halts. In contrast, the air stream caused continuous walking and induced a reaching response where the forelegs actively sampled the air. Such reaching increased the angular velocity and reduced walking speed, effects that were amplified in the presence of vapours from o -nitrophenol and methyl salicylate in the air flowing over the ticks. Vapour from a 1:1 mixture of o -nitrophenol and methyl salicylate was attractive over a 10⁴-fold concentration range providing an increase in upwind displacement of 20–40%, significantly higher than the natural ratio where o -nitrophenol vapour predominates. Although the responses to o -nitrophenol vapour were variable when presented alone, this chemical was consistently attractive when delivered with steer hair odour – unattractive on its own. Moreover, the upwind walk to this combination did not cause a change in speed or angular velocity. This supports the hypothesis that the response to the pheromone is enhanced by host odour. Accepted: 16 October 1999     

Continuous lipolysis in a reversed micellar membrane bioreactor

The enzymatic hydrolysis of olive oil using Chromobacterium viscosum lipase B encapsulated in reversed micelles of AOT in isooctane was carried out in a continous reversed micellar membrane bioreactor. A tubular ceramic membrane installed in an ultrafiltration module was used to retain the lipase and separate the products from the reaction media. Water filled micelles were supplemented to the reactor together with the substrate/solvent solution to compensate for the permeation of reversed micelles. The influence of substrate concentration, residence time and water content in the productivity and conversion of the system were investigated. A linear relationship between productivity and conversion degree was found for each substrate concentration tested. Operational stability of the bioreactor was tested in a long term operation confirming the high stability of this catalytic system.List of Symbols a(S ₀ ), b(S ₀ ) parameters of Eq. (3) - [AOT] mM AOT concentration - C _c mM concentration in the concentrate - C _p mM concentration in the permeate - E _t mg total amount of lipase - [lipase] mg/cm³ overall lipase concentration - [OIL] mM olive oil concentration - [OLEIC] mM oleic acid concentration in the permeate - P mol/(min · mg) oleic acid productivity - Q _in cm³/min inlet flow rate - Q _out cm³/min outlet flow rate (equal to permeate flow rate) - Q _r cm³/min recirculation flow rate - W _o ratio of water to AOT molar concentrations - X steady state conversion degree in the permeate stream - T °C temperature - rejection coefficient     

Variation in leaf respiration in relation to growth and photosynthesis of Lolium

Six Lolium genotypes with contrasting apparent photorespiration and CO_a compensation concentration, [C0₂]_c, were compared for net photosynthesis, dark respiration, leaf starch accumulation, rate of leaf expansion and shoot regrowth. Plants were grown in day/night temperatures of 15/10 and 25/20 ^oC. There were significant (P < 0–05) differences between the genotypes in all these parameters. At 25/20 ^oC apparent photorespiration was correlated with [CO₂]_c. Correlation coefficients, pooled from both temperature regimes, revealed that genotypes with high rates of net photosynthesis accumulated more leaf starch during light periods than genotypes with slow photosynthesis, but rates of leaf expansion and dry matter increase were only correlated, negatively, with dark respiration. Apparent photorespiration was negatively correlated with dark respiration. These findings suggest that attributes related to photorespiration such as [CO₂]_c and O₂ uptake from CO₂-free air in the light are unlikely to be useful selection criteria for growth of C₃ grasses, that net photosynthesis was probably not limiting growth and that maintenance respiration may have been an important determinant of genotypic differences in growth rate. Selections for slow and fast rates of dark respiration of mature leaves were therefore made at 8 and at 25 ^oC from within two different populations of L. perenne, S.23. This characteristic showed repeatabilities (broad-sense heritability) of from 0–41 to o-66. Six independent comparisons of simulated swards of the slow- and fast-respiring selections were made under periodic cutting regimes, either in a growth room at 25 ^oC or in a glasshouse from August to May. Growth of all plots of slow-respiring genotypes was consistently more rapid than that of the fast-respiring, at 25 ^oC in the growth room, and during autumn and spring in the glasshouse. There was no difference in winter growth. The implications of these results for the use of gas exchange measurements as selection criteria in plant breeding programmes are discussed.     

Bioconversion of acid-hydrolyzed poplar hemicellulose to acetic acid byClostridium thermoaceticum

Summary Clostridium thermoaceticum was used to ferment carbohydrate released from pretreated oat splet xylan and hemicellulose isolated from hybrid poplar. Hydrolysis with dilute sulfuric acid (2.5% (v/v) for oat spelt xylan and 4.0% (v/v) for poplar hemicellulose) at 100°C for 60 min was found to release the highest concentration of fermentable substrate.C. thermoaceticum, when grown in non-pH controlled batch culture at 55°C under a headspace of 100% CO₂, typically produced 14gl^–1 acetic acid during a 48 h fermentation in medium containing 2% xylose. In fed-batch fermentations this organism was able to produce 42gl^–1 acetic acid after 116h when the concentration of xylose was maintained at approximately 2% and the pH was controlled at 7.0.