Effect of temperature on growth characteristics of Bacillus cereus TZ415.

The effect of temperature on the maximal specific growth rate was studied in Bacillus cereus between 5 and 40 degrees C cultivated in courgette broth and rich medium (J broth). B. cereus grown from 5 to 38 degrees C in rich medium. No growth was observed in courgette broth below 10 degrees C. The Arrhenius plot was fitted from experimental data of B. cereus grown in rich medium and at regulated pH, oxygen and temperature. Two domains which are separated by a critical temperature around 13 degrees C can be distinguished with regard to temperature dependence of maximal specific growth rate. Over the cold domain from 5 to 13 degrees C, the temperature characteristic was 2.6 fold higher than over the sub-optimal domain from 13 to 38 degrees C suggesting that the growth temperature regulates several metabolic pathways.

Effect of horizontal clinorotation on the root system development and on lipid breakdown in rapeseed (Brassica napus) seedlings.

Seedlings of Brassica napus were cultivated on a slowly rotating clinostat (1 rpm) or in the vertical control for 5 d. The root growth, the cotyledonary reserves and the transport of 14C-labeled sucrose from cotyledons to root system were studied in both cultural conditions. The biomass (fresh weight) of the root system was 35% higher in the horizontally clinorotated seedlings than in the controls. This increase was correlated with a greater degradation of reserve lipids and faster accumulation of sucrose in the cotyledons. The activity of isocitrate lyase, one of the two enzymes necessary to conversion of lipids into glucids, was also greater in the cotyledons of clinorotated seedlings. The labeling distribution of 14C in the cotyledons, the hypocotyl and the root system after 30, 60 and 120 min of application of 14C-labeled sucrose on the cotyledons showed higher translocation of the cotyledonary sucrose to the root system of clinorotated seedlings. In addition, we studied the effects of clinorotation on the biomass of the excised root system (of 10 d old seedlings) cultivated in a medium containing 1% sucrose. The horizontally clinorotated root system grew more than that of the controls. These results showed that the horizontal clinorotation acted on the root system growth and provoked a higher sucrose translocation from source to sink, i.e. from cotyledons to root system.

Large-scale preparation of (Z)-3-hexen-1-yl acetate using candida antarctica-immobilized lipase in hexane

A kilogram-scale synthesis of (Z)-3-hexen-1-yl acetate, in hexane, on direct esterification of (Z)-3-hexen-1-ol with acetic acid in the presence of 2% (w/w reactants) of an immobilized lipase from Candida antarctica (Novozym 435) is reported. Conversion yields ranging from 92 to 96% were obtained after optimization of various parameters. In that respect, elimination of the water proved crucial. Using at both the laboratory large scale (preparation of 200-400 g of ester) and the pilot scale (1-5 kg) a "reflux" rotary evaporator equipped with a graduated decantation flask, we were able to trap the water evolved during esterification while at the same time monitor the time course of the reaction. As a consequence of both an efficient water trapping and of a gentle dispersion of the immobilized lipase into the reaction medium, the lifetime of the enzyme was significantly prolonged. At the laboratory large scale (LLS), the yield was still >/=90% after seven consecutive utilizations whereas at the pilot scale (PS), it reached 93% after reusing the enzyme four times. In those conditions, the amount of immobilized enzyme necessary to produce 1 kg of (Z)-3-hexen-1-yl acetate was 18 g (1. 8%) and 60 g (6%) at the LLS and the PS, respectively. Copyright 1998 John Wiley & Sons, Inc.