Some factors affecting spore replication of Nosema algerae (Microspora,Nosematidae) in Pieris brassicae (Lepidoptera)

The production of Nosema algerae spores was examined in Pieris brassicae. Spore replication in the insect host followed a logistic pattern of development. The factors studied which affected spore production and replication were dose level (5 × 10², 5 × 10³, and 5 × 10⁴ spores per insect), larval instar (fourth and fifth), and cool pretreatment of the insects at 20°C prior to inoculation compared with a constant temperature of 26°C. A three-way analysis showed the interactions between these factors. The logistic pattern of spore replication was used to explain the results.     

Isolation,culture and regeneration of protoplasts from birdsfoot trefoil (Lotus corniculatus)

A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus L. cv. Leo). Green cotyledons from in vitro grown seedlings were preplasmolyzed in CPW salts containing 13% mannitol (CPW 13 M) for 1 h prior to the enzyme treatment. The enzyme formula consisted of 2% (w/v) Onozuka Cellulase R-10, 1% (w/v) Macerase and 0.1% (w/v) Pectolyase Y-23 in CPW 13 M. This method produced high yields of viable protoplasts after purification. The procedure is reproducible and takes approximately 2.5 months from protoplast isolation to plantlet establishment in a greenhouse. More than 100 plantlets were grown in soil. Two somaclonal variants, a chimeric plant for chlorophyll production and an albino cell line, have been obtained by this procedure.     

低温预处理过程中大麦花药内源激素的变化

很多文章曾报道低温预处理可以明显提高大麦花药反应频率。但对于低温预处理的机理,至今研究报道甚少。我们应用ＥＬＩＳＡ方法测定了大麦花药低温预处理过程中内源激素ＩＡＡ、ｉＰＡ和ＡＢＡ含量。根据实验结果,推测低温预处理改变了花药内源ＩＡＡ和ｉＰＡ含量,阻断了花粉原来的发育方向,使其由配子体的发育途径转向孢子体的发育途径。     

Enzymatic hydrolysis of lignocellulosic materials: II. Experimental investigations of theoretical hydrolysis--process models for an increased enzyme recovery

Stream pretreatment of wheat straw solubilized most of the xylan present. Xylose and other sugars were recovered by washing the substrate with water but only a minor part (34%) was monomeric. Treatment of this solutions with celulases and hemicellulases improved the yield of monomeric sugars to 69%, the main product being xylose. Some xylose was also obtained during enzymatic hydrolysis of the solid substrate although the pretreatment step contributed 64% (mean value) of total xylose formed. A reference model, No. 1, and two other models, Nos. 2 and 4, described in the first part of this article series (this issue) have been studied experimentally and results confirm the theoretical conclusions. An uninterrupted hydrolysis over a given time period leads to a lower degree of saccharification than when hydrolysate is withdrawn several times. Saccharification is also favored if the residue is removed at a late stage, i.e., at the end of the 24 h hydrolysis cycle. Extended recirculation of the enzymes during a 4 x 24-h experimental period gave the following average yields of saccharification on a 24-h basis: 65% (Reference), 73% (Model 2), and 79% (Model 4). It is concluded that enzyme recovery with model 4 is 70% or more, while the Reference and Model 2 attain a lower level of recovery. The design of an improved hydrolysis model is also discussed.     

Effects of electroconductive heat treatment and electrical pretreatment on thermal death kinetics of selected microorganisms

Suspensions of yeast cell (zygo Saccharomyces bailii) in a phosphate buffer solution were subjected to conventional (hot water) and ohmic (electric current) heating under identical temperature histories. Experiments were also conducted with cells of Escherichia coli to compare the lethal effect of combination of sublethal electrical preteatment and conventional heating with conventional heating. The kinetic parameters (D,Z,K and E(a)) were determined for both organisms during different treatments. There was no significant difference in the death rate of yeast cells during conventional and ohmic heating at the voltage range used in this study. Results of electrical pretreatment and conventional heating on E. coli indicated differences under certain conditions when compared with pure conventional heating. Thus it is concluded that microbial death during ohmic heating was due primarily to thermal effects with no significant effect of electric current per se. Sublethal electrical pretreatment appears to offer potential for increased bacterial inactivation in certain cases.     

Effects of lignin content on the properties of lignocellulose-based biocomposites

The paper is focused on the analysis of the behaviour of biocomposites (biodegradable composites) which are reinforced with different fillers fractions, with varying lignin contents. These materials have been carried-out by extrusion and injection moulding. The matrix, an aromatic copolyester (polybutylene adipate-co-terephthalate), is biodegradable. The lignocellulose fillers are a by-product of an industrial fractionation process of wheat straw. From the raw agro-material and by lignin extractions, various fillers fractions have been obtained by varying the fractionation conditions, both on the liquid media (aqueous or organic) and on the temperature. The fillers lignin contents vary from 30 to 14 wt% with a resultant increase of the cellulose content. We have analysed the impact of the different extraction conditions on the fillers surface and size distribution, and also on the final thermal and mechanical properties of the biocomposites. These materials present significant differences of behaviour which can fulfil some requirements for applications, such as non-food packaging or other short-lived applications (agriculture, sport …) where long-lasting polymers are not entirely adequate.     

Improvement of Nonradioactive DNA in Situ Hybridization

With the introduction of microwave pretreatment, the quality of nonradioactive in situ hybridization (NISH) using DNA probes on formalin fixed tissue has significantly improved. Even after microwave treatment, however, there are cases where NISH results remain unsatisfactory. Therefore, we tried to improve NISH by testing other buffer systems as alternatives to the citrate buffer that is routinely applied during microwave pretreatment. By using buffer systems originally designed for immunohistochemistry, we significantly improved our NISH results. Difficult tissue samples were more accessible to NISH using these alternative buffer systems and made the quantitative evaluation easier. These results may also be of interest for combined applications of NISH and immunohistochemistry.     

Optimization of integrated alkaline–extrusion pretreatment of barley straw for sugar production by enzymatic hydrolysis

In this work, an integrated one-step alkaline–extrusion process was tested as pretreatment for sugar production from barley straw (BS) biomass. The influence of extrusion temperature (T) and the ratio NaOH/BS dry matter (w/w) (R) into the extruder on pretreatment effectiveness was investigated in a twin-screw extruder at bench scale. A 2³ factorial design of experiments was used to analyze the effect of process conditions [T: 50–100 °C; R: 2.5–7.5% (w/w)] on composition and enzymatic digestibility of pretreated substrate (extrudate). The optimum conditions for a maximum glucan to glucose conversion were determined to be R = 6% and T = 68 °C. At these conditions, glucan yield reached close to 90% of theoretical, while xylan conversion was 71% of theoretical. These values are 5 and 9 times higher than that of the untreated material, which supports the great potential of this one-step combined pre-treatment technology for sugar production from lignocellulosic substrates. The absence of sugar degradation products is a relevant advantage over other traditional methods for a biomass to ethanol production process since inhibitory effect of such product on sugar fermentation would be prevented.