Scleroglucan and oxalic acid formation by Sclerotium glucanicum in sucrose supplemented fermentations

Summary Strategies for adding sucrose to stationary phase cultures of Sclerotium glucanicum to improve scleroglucan production were examined. Particular attention was paid to the effect of sucrose supplementation on the formation of the toxic by-product, oxalic acid. The rate of addition of sucrose was found to markedly influence the outcome of the process, with addition at a rate of 0.084 gl^–1h^–1 giving a 50% improvement in broth biopolymer concentration. Additions at higher rates seemed to cause inhibition of the culture. However, greatly increased oxalic acid concentrations in the sucrose supplemented fermentations, and the impact of unfavourable changes in productivity and specific productivity call into question the utility of this proposed method of process improvement for this microorganism.     

Physical and physiological factors in diapause initiation of two hyperparasites of the tobacco hornworm,Manduca sexta

Hypopteromalus tabacum diapauses as a last larval instar and Catolaccus aeneoviridis as a non-pharate pupa within cocoons of the primary parasite, Apanteles congregatus. Four factors (photoperiod, temperature, maternal age, and physiological state of the host) were tested for their significance in diapause initiation of both species. A 10L : 14D photoperiod produced a higher incidence of diapausing individuals than a 13L : 11D photoperiod. In the temperature range from 18 to 24°C, the incidence of diapause was inversely related to temperature. The incidence of progeny entering diapause varied with the age of the mother, younger ones producing fewer diapausing offspring. An increase in the number of C. aeneoviridis entering diapause was observed when the host, A. congregatus, was in the diapausing, rather than the nondiapausing condition. Analysis of the data indicated that interactions between these four factors also played an important rôle in diapause initiation of both species.