Effect of water activity and protective solutes on growth and subsequent survival to air-drying of Lactobacillus and Bifidobacterium cultures

Probiotic cultures of Lactobacillus plantarum, Lactobacillus rhamnosus, Bifidobacterium longum, Lactobacillus casei and Lactobacillus acidophilus were grown in media having water activities (a _w) adjusted between 0.99 and 0.94 with NaCl or with a mixture of glycerol and sucrose in order to find conditions of osmotic stress which would still allow for good growth. Cultures grown at a _w?=?0.96 or 0.99 were then recovered by centrifugation, added to a sucrose–phosphate medium and air-dried. In some assays, a 2-h osmotic stress was applied to the cell concentrate prior to air-drying. Assays were also carried out where betaine, glutamate and proline (BGP) supplements were added as protective compounds to the growth or drying media. For most strains, evidence of osmotic stress and benefits of BGP supplementation on growth occurred at a _w?=?0.96. Growing the cells in complex media adjusted at a _w?=?0.96 did not enhance their subsequent survival to air-drying, but applying the 2-h osmotic stress did. Addition of the BGP supplements to the growth medium or in the 2-h stress medium did not enhance survival to air-drying. Furthermore, addition of BGP to a sucrose–phosphate drying medium reduced survival of the cultures to air-drying. This study provides preliminary data for producers of probiotics who wish to use air-drying in replacement of freeze-drying for the stabilization of cultures.     

Development of pilot-scale fermentation and stabilisation processes for the production of microsclerotia of the entomopathogenic fungus Metarhizium brunneum strain F52

Using 100 L stirred-tank bioreactors, we evaluated the effect of fermentation parameters and drying protocols on the production and stabilisation of microsclerotia (MS) of the entomopathogenic fungus Metarhizium brunneum (formerly M. anisopliae F52). Results showed that stirred-tank bioreactors can be used to mass produce stable MS of Metarhizium and that culturing and drying protocols significantly affected MS yield and stability. Length of fermentation (4–7 days) for Metarhizium cultures had no significant impact on biomass accumulation, MS formation or the storage stability of the air-dried MS granules. Although cultures of Metarhizium grown on media with a carbon-to-nitrogen (C:N) ratio of 30:1 produced significantly more biomass when compared to cultures grown in media with a C:N ratio of 50:1, MS formation and desiccation tolerance following drying were similar. After storage for 1 year at 4°C, conidia production by air-dried MS granules from 50:1 media was significantly higher compared to MS granules from 30:1 media. The addition of diatomaceous earth (DE) to cultures of Metarhizium prior to drying at rates of 0–60 g L^?1 had no significant effect on MS desiccation tolerance but did impact conidia production. Air-dried MS granules without DE produced significantly more conidia g^?1 during the first 4 months of storage, but after 1 year, conidia production was similar regardless of DE content of the MS granule. Microsclerotial granules with higher moisture levels (2.6–5.0% w/w) produced significantly more conidia immediately after drying and MS granules with low moisture (0–2.5% w/w) produced more conidia after 12 months storage.     

Drying and formulation of blastospores of Paecilomyces fumosoroseus (Hyphomycetes) produced in two different liquid media

Formulation matrices can play an important role in improving the storage survival and biocontrol efficacy of microorganisms used for the control of pest insects. In this study, liquid culture-produced blastospores of the entomopathogenic fungus Paecilomyces fumosoroseus were formulated with different inert and organic materials prior to air-drying. Paecilomyces fumosoroseus blastospores were produced in two different liquid media, a basal salts medium supplemented with Casamino acids and glucose (LM1) and a medium containing peptone of collagen and glucose (LM2). Blastospores produced in the two test media were formulated with various supports. The formulation supports were cornstarch, rice flour, talc powders, Mexican lime, calcined kaolin clay, and diatomaceous earth. Several of the supports were tested at different concentrations. The initial and long-term (after storage at 4 and 28 °C) survival of the formulated, air-dried blastospores were evaluated. Initial blastospore viabilities were affected by the formulation material and by the blastospore production medium. Medium composition, drying support and storage temperature had an impact on the long-term survival of the blastospores. Under the conditions of the study, LM1 produced higher concentrations of blastospores that not only survived drying better than blastospores produced in LM2 but also maintained viability longer during storage in the formulation supports tested. The nature of the drying supports was shown to have a significant impact on the storage stability of all blastospores, particularly those produced in LM1. Under the production, drying and storage conditions used in the study, calcined kaolin clay formulations stored at 4 °C had the best storage stability. In all formulations tested, spore survival over time was reduced for blastospore formulations stored at 28 °C rather than 4 °C.     

The effects of some storage conditions on viability of Lecanicillium lecanii conidia to whitefly (Homoptera: Trialeurodes vaporariorum)

A study on the survival of Lecanicillium lecanii conidia in storage at room temperature was carried out. Firstly, drying methods of conidia powder were compared. Vacuum-freeze drying (VFD) was more suitable for drying conidia as compared to vacuum drying (VD) at room temperature. Vacuum-freeze drying for 24-h resulted in a water content of 5.4%, and a viability, determined as germination of conidia in 2% glucose solution after16 h, was 90.3% and the infection in greenhouse whitefly, Trialeurodes vaporariorum was about 94.7% at a dose of 1×10⁸ conidia/mL. Secondly, the factors influencing viability of conidia stored at room temperature were evaluated in the laboratory. Temperature was the most critical factor influencing conidial storage stability, among the tested factors affecting survival of conidia stored at room temperature for 6 months. Both conidial germination and infection of hosts decreased with storage temperature increasing from 15 to 35°C, and at 35°C the survival of stored conidia for 6 months was near zero. The moisture content of the conidial powder was another major factor influencing viability of stored conidia at room temperature. Conidial powder dried to about 5% moisture content showed higher viability than non-dried conidial powder. For the carriers, clay and charcoal were more suitable for storage of L. lecanii conidia at room temperature. At a room temperature of 25°C, L. lecanii conidia which were dried to 5% water content and mixed with clay or charcoal could retain about 50% survival after 6 months' storage.     

Heat-shock response in a yeast tps1 mutant deficient in trehalose synthesis

Exponential cells of the Saccharomyces cerevisiae tps1 mutant underwent a rapid loss of viability upon a non-lethal heat exposure (from 28 to 42°C). However, a further more severe heat stress (52.5°C 5 min) induced an increase in the fraction of viable cells. This mutant can not synthesize trehalose either at 28° C or at 42°C due to the lack of a functional trehalose-6P synthase complex. In control experiments carried out with the wild-type W303-1 B, heat-stressed exponential phase cultures grown on YPgal at 28°C acquired thermotolerance to a higher extent than identical cultures grown on YPD, although in both cultures the level of stored trehalose was negligible. These data suggest that the bulk of trehalose accumulated in yeast upon mild heat treaments is not sufficient to account for the acquisition of thermotolerance.     

Effect of different drying procedures on the nutritive value of olive (Olea europaea var. europaea) leaves for ruminants

Fresh, freeze-, air- and oven-dried at 60 °C and 100 °C olive leaves (OL) were studied in order to determine the effect of different drying procedures on OL chemical composition, in vitro digestibility, ruminal degradability, and intestinal digestibility. The drying procedure affected all the parameters measured except for gross energy (GE; P=0.194). Protein-bound condensed tannins (CT) decreased (P=0.001) with freeze-, air- and 60 °C drying (from 1.25 up to 0.82 g/kg dry matter, DM). Total CT were only decreased (P=0.001) by drying at 60 °C (from 10.0 to 6.24 g/kg DM). The in vitro crude protein (CP) digestibility increased (P<0.001) with drying except for oven-drying at 100 °C up to 58%. Values for CP digestibility found in freeze- and air-dried OL were not different (P>0.05). No differences (P>0.05) were observed between CP digestibility in air- and oven-dried at 60 °C OL. Effective degradability of DM and CP increased from 0.53 to 0.62 (P=0.005) and from 0.46 to 0.64 (P=0.002), respectively after treatment. The apparent intestinal digestibility of undegraded CP in the rumen was only affected (P=0.046) by oven-drying, which increased it from 0.33 to 0.39. As air-drying did not have detrimental effects on the OL nutritive value it could be an appropriate, simple and low-cost procedure for olive-leaves preservation.     

Survival of cultured cells in the cold : A kinetic study with special reference to the effect of serum in culture media

The survival at 4 °C of mouse fibroblasts (strain L-929) and rat liver cells (strain JTC-25·P5) was kinetically analysed after they had been pre-incubated at 37 °C in medium with or without supplement of serum. Both the composition of medium used for preincubation at 37 °C and that employed for storage at 4 °C had influence on the survival period.When the cells had been grown at 37 °C in Eagle minimal essential medium (MEM) alone, they rapidly lost their viability at 4 °C from the beginning. However, when grown at 37 °C in MEM supplemented with calf serum, they maintained viability at 4 °C for about 16 days and 8 days for L cells and JTC-25·P5 cells respectively, before the initiation of rapid loss of viability. The presence of macromolecular fraction of calf serum in the medium during preincubation was found to be responsible for the prolongation of survival at 4 °C.     

Impact of mild heat treatments on induction of thermotolerance in the biocontrol yeast Candida sake CPA-1 and viability after spray-drying

Aims: The objective of this study was to examine the induction of thermotolerance in the biocontrol agent Candida sake CPA‐1 cells by mild heat treatments to enhanced survival of formulations using spray‐drying. The possible role of heat‐shock proteins (HSPs) biosynthesis in induced thermotolerance and the role of sugars and sugar alcohols were also determined. Methods and Results: Studies were conducted on C. sake cells grown in molasses medium and exposed to mild temperatures of 30 and 33°C during mid‐ (16 h), late‐exponential (24 h), early‐ (30 h) and mid‐stationary (36 h) growth phases. The effect on viability was determined both before and after spray‐drying. Cycloheximide and chloramphenicol were used to examine the role of HSPs and HPLC was used to analyse the accumulation of sugar and sugar alcohols. The results indicate that both temperatures induced thermotolerance in cells of C. sake. Mild heat‐adapted cells at 33°C in the early‐ or mid‐stationary phases had survival values after spray‐drying significantly higher (P ≤ 0·05) than nonadapted cells. However, viabilities were not high enough to be considered for commercial use with values up to 17%. HSPs were not implicated in thermotolerance acquired by mild heat‐adapted cells as similar viabilities were obtained in the presence of protein inhibitors. Little change was observed in sugar and sugar alcohols with an increase in glucose and arabitol in some treatments. Conclusions: This study suggests that it is possible to induce thermotolerance in biocontrol yeasts such as C. sake. However, this does not improve survival of cells exposed to spray‐drying sufficiently to consider this a suitable formulation method for this biocontrol agent. HSPs, sugars and sugar polyols were not directly responsible for induced thermotolerance in yeast cells. Significance and Impact of the Study: This type of information can be effectively applied to improve the viability of cells in the process of formulation.     

Induction of heat sensitivity of wheat roots and its effects on mitochondria, adenosine triphosphate, triglyceride, and total lipid content

Wheat seedlings were subjected to heat shock for 2 min at 45 °C. After heat treatment, the wheat seedlings were incubated at 25 or 35 °C. At 25 °C, but not at 35 °C, the root tips survived the heat shock. Immediately after the heat treatment the free triglyceride content in the treated root tips was higher than in the untreated roots, but the total lipid content was not changed. The ATP content immediately after the heat treatment was variable, but after about 1 h it stabilized at the same level as in the control or at a higher level. After 45 min at 25 °C after heat shock, the endoplasmic reticulum cisternae had expanded, giving rise to small irregular vacuoles. Golgi vesicles were also irregular. Four hours after heat treatment the endoplasmic reticulum and Golgi vesicles again were normal, but mitochondria were irregular with fewer tubules and with adhering membrane curls containing lipids. These membrane curls were not observed 24 h after heat treatment. When incubated at 35 °C after heat shock wheat root meristems died. Some cells in the meristem were still alive 4 h after treatment. They had large vacuoles with membrane whorls and plasmalemmasomes, and in some cases the cells were partly lysed.     

Polysaccharide production benefits dry storage survival of the biocontrol agent Pseudomonas fluorescens S11:P:12 effective against several maladies of stored potatoes

Pseudomonas fluorescens S11:P:12 (NRRL B-21133) is a biological control agent able to suppress several potato diseases and sprouting. Notably, it produces a polysaccharide during liquid cultivation, and the objective of this work was to determine the role of this material in the bio-control process. First, the polysaccharide was isolated, purified and identified as marginalan, which accumulated to ~3.3 g/L in cultures. The bioactivity of isolated marginalan applied alone or in combination with washed cells of strain S11:P:12 was tested in potato bioassays of dry rot and pink rot suppressiveness and sprout inhibition. Since the formulation and storage of a dried biocontrol product is preferred for commercial use, the impact of marginalan on cell survival during drying and storage was also studied. Washed bacteria formulated with 0–6.6 g/L polysaccharide were either applied to Hyflo granules, then slowly dried for 24 h with airflow at 50–60% relative humidity, or in 1-µL droplets placed in replicate wells of a micro-plate, then quickly dried for 1 h in a biohazard hood. Both Hyflo and micro-plate dry storage results indicated that marginalan significantly reduced cell death after drying, such that the final stable viable cell density was 2.5–5 orders of magnitude greater, respectively, than if no marginalan were included with cells. Marginalan had no significant impact on disease or sprout suppression by strain S11:P:12, and its main benefit to biocontrol was viable cell preservation during drying and storage. When marginalan was formulated with other selected P. fluorescens strains, its benefits to drying and storage survival were again evident (especially after 4°C instead of 25°C storage), but its effects were more subtle than for strain S11:P:12, and dry rot suppression was not impacted.     

Mass Production Potential of the Bacto-Helminthic Biocontrol Complex Heterorhabditis indica - Photorhabdus luminescens

Heterorhabditis indica is a potential agent for the biological control of grubs in sugarcane fields in India. The type strain LN 2 was transferred to monoxenic cultures on its symbiont Photorhabdus luminescens and successfully produced on solid media. In liquid cultures, a mean dauer juvenile yield of 457 000 was obtained with a maximum of 648 000 per ml. Comparatively high yields have not been reported before. Therefore, costs related to the liquid culture production of H. indica will be lower than for other entomopathogenic nematodes currently used in biocontrol. Different bacterial clones had no significant influence on the dauer juvenile yields in liquid media. The exit from the dauer juvenile stage (recovery) after inoculation and the number of hermaphrodites significantly decreased when culture temperature was increased from 25-30 ° C; the dauer juvenile yields were not affected. The cell density of P. luminescens in batch cultures was higher at 25 and 30 ° C than at growth temperatures of 35 and 37 ° C. In continuous culture, the bacterial growth was inhibited when the growth temperature reached 38 ° C. After approximately 60 h, the bacteria adapted to higher temperature and the growth rate increased again. When the temperature was further increased to 40 ° C, the bacterial growth was inhibited.     

Effects of trehalose on stress tolerance and biocontrol efficacy of Cryptococcus laurentii

AIMS: To investigate the effects of internal trehalose on viability and biocontrol efficacy of antagonistic yeast Cryptococcus laurentii under stresses of low temperature (LT), controlled atmosphere (CA) and freeze drying. METHODS AND RESULTS: The content of trehalose in C. laurentii was increased by culturing the yeast in trehalose-containing medium. Compared with yeast cells with low trehalose level, the yeast cells with high level of internal trehalose not only obtained higher viability, but also showed higher population and better biocontrol efficacy against Penicillium expansum on apple fruit both at 1 degrees C and in CA condition (5% O(2), 5% CO(2), 1 degrees C). After freeze drying, survival of the yeast with high trehalose level was markedly increased when stored at 25 degrees C for 0, 15 and 30 days. Meanwhile, high integrity of plasma membrane was detected in the freeze-dried yeast with high trehalose level by propidium iodide staining. CONCLUSIONS: Induced accumulation of internal trehalose could improve viability and biocontrol efficacy of C. laurentii under stresses of LT and CA. Moreover, survival of the yeast was also increased as internal trehalose accumulation after freeze drying, and one of the reasons might be that trehalose gave an effective protection to plasma membrane. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this experiment show a promising way to improve the biocontrol performance of antagonistic yeasts under the commercial conditions.     

ENVIRONMENTAL FACTORS AFFECTING RESISTANCE TO DESICCATION IN THE DIATOM STAURONEIS ANCEPS

Several environmental parameters influence the ability of Stauroneis anceps Ehr. to survive periods of dehydration to equilibrium with atmospheric humidity. Cells grown in soil-water are better able to survive desiccation than cells grown in defined medium and cells from older cultures survive better than those from young cultures. Since active culture growth and cell division do not hinder survival, the factor responsible for increased survival in older cultures may be the accumulation of secreted metabolites in the medium. There is no survival when drying occurs in artificial substrata with particles 50 microns or less in diameter. Survival occurs when the particulate matter is 100 microns or larger. Slow drying seems to enhance survival, perhaps by allowing cells to interact longer with environmental organic substances conferring some degree of protection. Desiccated cells are better able to withstand temperature extremes than are vegetative cells in an aqueous environment. Dry cells survived longer than 9 days at 60 C and longer than 8 hr at 80 C but normal cultures were unable to survive 1 hr at 60 C. Temperatures of —15 to —20 C were also sustained more consistently by desiccated cells. Cells stored at vapor pressure deficits of 11.9 mm Hg or higher survived longer than 16 months but storage at 5.9 mm Hg or lower reduced survival time.     

Population dynamics of the Fusarium head blight biocontrol agent Cryptococcus flavescens OH 182.9 on wheat anthers and heads

Cryptococcus flavescens OH 182.9 (NRRL Y-30216) reduces Fusarium head blight (FHB) incited by Fusarium graminearum and deoxynivalenol (DON) contamination of grain. Yet little is known about the population dynamics of OH 182.9 on wheat heads and anthers. Biomass of OH 182.9 was produced in liquid culture and applied to greenhouse and field grown wheat prior to and during early anthesis. In greenhouse studies, populations of OH 182.9 were similar on anthers for heads inoculated before (Feekes 10.5) or early in flowering (Feekes 10.5.1) but were 1–3 log units lower in Feekes 10.5 inoculated wheat after 8–10 days. In greenhouse and field studies, OH 182.9 colonized anthers inside florets prior to anthesis. In the field, populations of OH 182.9 on anthers increased or, less frequently, remained stable through 12 days, regardless of application time and peaked at 1–2 log units higher than in the greenhouse. Strain OH 182.9 reduced FHB severity (P < 0.05, FPLSD) but not other disease parameters in the same field study. Application of OH 182.9 at split boot (Feekes 10.1) or Feekes 10.5.1 resulted in higher populations on spikelets treated at flowering on a CFU/g fresh weight tissue basis and as a percentage of the total recoverable microbial population in one of two field studies. Scanning electron microscopy revealed cells of OH 182.9 in microcolonies, groups of several cells and as individual cells, most frequently on the abaxial surfaces of glume and lemma tissues and near the apex of palea tissues. The survival of yeast OH 182.9 on anthers and wheat heads for 12 days and more suggests the strain has the potential to reduce late kernel infections by F. graminearum that can increase DON.     

Effect of the pH of growth on the survival of Lactobacillus delbrueckii subsp. bulgaricus to stress conditions during spray-drying

AIMS: The aim of this study was to optimize survival of Lactobacillus delbrueckii subsp. bulgaricus during spray-drying and subsequent storage through optimizing the pH of growth conditions. METHODS AND RESULTS: Cell concentrates previously grown without or with pH controlled were spray-dried and stored at 20 degrees C and heat treated at 57 degrees C. Cells grown under noncontrolled pH were more resistant to both drying and heating than cells grown under controlled pH but no significant differences were observed during storage. The intracellular proteins profile of cells grown under both conditions was studied by two-dimensional SDS-polyacrylamide gel electrophoresis. Eight proteins were identified using automated mass spectrometry (MS) and tandem mass spectrometry (MS/MS) data acquisition. Of the identified proteins, only cochaperonin GroES corresponded to a known heat shock protein (HSP). The other proteins identified are proteins involved in glycolysis. For cells grown under noncontrolled pH the expression of the Hsp70, GroES and GroEL, measured by Western blotting, was enhanced. CONCLUSIONS: The higher resistance of cells grown under noncontrolled pH correlates with the enhanced production of heat shock proteins. SIGNIFICANCE AND IMPACT OF THE STUDY: Growth of L. bulgaricus under controlled pH (commonly used by the starter cultures production industry) results in cells more sensitive to stresses frequently encountered by the cells during starter cultures preparation/storage/utilization.     

Effect of temperature on the longevity of human fibroblasts in culture

The longevity of parallel cultures of the human diploid fibroblast strain MRC-5 was measured at various incubation temperatures. At 37°C the mean life-span was 57.2 passages, at 34°C it was 58.7 passages and at 40°C it was 29.2 passages. There was greater variation in longevity among cultures grown at 40°C than in the control population and least among those grown at 34°C. The decreased life-span at 40°C was probably due to accelerated ageing, as the transfer of senescent cultures back to 37°C did not lead to their recovery. Cultures grown at 32°C also had reduced life-span compared to the control, but this was probably not the result of ageing, as the transfer of cultures which had almost ceased growth back to 37°C allowed them to reach the normal life-span for this temperature. The results imply that clonal ageing is at least in part due to random events—possibly errors in protein synthesis—which occur more frequently with increasing temperature.     

Survival of the postharvest biocontrol yeast Candida sake CPA-1 after dehydration by spray-drying

Spray drying was evaluated as a dehydrating method to preserve the postharvest biocontrol agent Candida sake CPA-1. The effect of drying temperature, carrier, growth and rehydrating medium on the survival of the yeast was studied. Outlet temperature had more influence on the death of the cells than inlet temperature, and survival decreased with increasing temperature. Spray drying at an inlet temperature of 150°C was optimum in terms of viability, powder recovery and moisture content of the product. Use of 10% (v/v) skimmed milk as a carrier gave the highest survival and percentage of powder recovery (34-47%). Rich rehydration media were found to be better than water or phosphate buffer, with slight differences on survival. Spray-dried cells were less effective than fresh ones in controlling Penicillium expansum rot on apples. Spray drying of C. sake was not a good dehydration method as it gave low cell survival, poor recovery of product, and low efficacy.     

A temperature-sensitive mutant of cultured mouse cells defective in chromosome condensation

A temperature-sensitive mutant, designated ts85, was isolated from a mouse mammary carcinoma cell line, FM3A. The ts85 cells grew at 33 °C (permissive temperature) with a doubling time of 18 h, which was almost the same as with wild-type cells, whereas the cell number scarcely increased at all at 39 °C (non-permissive temperature). When the ts85 cells were shifted from 33 to 39 °C, their DNA synthesis fell to below 1% of the initial value in 14 h. RNA or protein synthesis, however, was maintained at the initial levels for at least 14 h at 39 °C. Cytofluorometric analysis of asynchronous cultures and studies with synchronous cultures suggested that the bulk of the cells cultured at 39 °C for 12–18 h were arrested in late S and G2 phases. Electron microscopic observations revealed that chromatin was abnormally condensed into fragmented and compact forms, particularly around nucleoli, in about 80% of cells of an asynchronous culture incubated at 39 °C for 16 h. Cells in mitosis were not detected in such cultures and nuclear membrane and nucleoli were still intact. Such abnormal chromosome condensation was not observed in the ts85 cells at 33 °C or in wild-type cells at either temperature. Since these findings suggest that a ts gene product of ts85 cells is necessary for chromosome condensation, ts85 cells may represent a useful tool for establishing the mechanisms of chromosome condensation. The interrelationship between abnormal chromosome condensation and reduction in DNA synthesis of the ts85 cells is discussed.     

Temperature-dependent Development of Four Egg Parasitoid Trichogramma Species (Hymenoptera: Trichogrammatidae)

Trichogramma species have been successfully utilized for biocontrol of several lepidopteran pests worldwide. The development, survival and progeny production of two Kenyan species' Trichogramma bournieri Pintureau & Babault and Trichogramma sp. nr. mwanzai Schulten & Feijen (collected from Kenya), Trichogramma evanescens Westwood (Germany) and Trichogramma chilonis Ishii (India) was studied at four constant temperatures (13, 18, 25 and 34°C) with the 011 aim of assessing the relative biotic potential of the two native species for 011 biocontrol of Helicoverpa armigera and Plutella xylostella in Kenya. The study was conducted at the Institute 011 for Biological Control (BBA), Darmstadt, Germany. The Trichogramma species tested showed variations 011 in fertility, developmental time, percent emergence, progeny production and sex ratio 011 at the four temperature regimes. Fertility decreased as temperature increased from 25 to 34°C. 011 T. chilonis and T. evanescens completed development at all temperatures tested, but T. 011 bournieri and T. sp. nr. mwanzai failed to complete development at 13°C. The developmental 011 period for all the species decreased as the temperature increased. The duration of development from 011 oviposition to adult emergence varied from 8 days to 12 weeks shorter at 34°C than at 011 13°C for T. chilonis and T. evanescens . For the various temperatures tested, a linear model was 011 satisfactory for egg to adult development at P = 0.05 for T. chilonis and T. evanescens . The 011 lower temperature thresholds for development and duration in degree-days were 8.83°C and 188 for 011 T. chilonis and 9.23°C and 192 for T. evanescens , respectively. For all temperatures tested, 011 T. sp. nr. mwanzai had the highest preimaginal survivorship. Adult emergence was lower at 13°C and 34°C than at 011 18 and 25°C. The highest fertility (mean ±SE) (50.37 ±2.32 adult 011 female -1 ) and progeny production (44.03 ±2.02 adult female -1 ) was recorded at 25°C for 011 T. evanescens . Sex ratio was biased towards female at all temperatures in T. bournieri and T. chilonis . 011 At all temperatures tested, T . sp. nr. mwanzai produced more males than females. For all species tested, 011 favourable parasitism was between 18 and 25°C. The results from this study will be useful for mass rearing purposes as well as for future field release programmes.     

Gelatinization mechanism of potato starch

The non-Newtonian behavior and dynamic viscoelasticity of potato starch (Jaga kids red ’90, 21.0% amylose content) solutions after storage at 25 and 4°C for 24 h were measured with a rheogoniometer. The flow curves, at 25°C, of potato starch showed plastic behavior >1.0% (w/v) after heating at 100°C for 30 min. A gelatinization of potato starch occurred above 1.0% at room temperature. A very large dynamic viscoelasticity was observed when potato starch solution (3.0%) was stored at 4°C for 24 h and stayed at a constant value with increasing temperature. A small dynamic modulus of potato starch was observed upon addition of urea (4.0 M) at low temperature (0°C) even after storage at 25 and 4°C for 24 h. A small dynamic modulus was also observed in 0.05 M NaOH solution. Possible models of gelatinization and retrogradation mechanism of potato starch were proposed.