The influence of pH, temperature and carbon source (glucose and maltose) on growth rate and ethanol yield of Dekkera bruxellensis was investigated using a full-factorial design. Growth rate and ethanol yield were lower on maltose than on glucose. In controlled oxygen-limited batch cultivations, the ethanol yield of the different combinations varied from 0.42 to 0.45 g (g glucose)(-1) and growth rates varied from 0.037 to 0.050 h(-1). The effect of temperature on growth rate and ethanol yield was negligible. It was not possible to model neither growth rate nor ethanol yield from the full-factorial design, as only marginal differences were observed in the conditions tested. When comparing three D. bruxellensis strains and two industrial isolates of Saccharomyces cerevisiae, S. cerevisiae grew five times faster, but the ethanol yields were 0-13% lower. The glycerol yields of S. cerevisiae strains were up to six-fold higher compared to D. bruxellensis, and the biomass yields reached only 72-84% of D. bruxellensis. Our results demonstrate that D. bruxellensis is robust to large changes in pH and temperature and may have a more energy-efficient metabolism under oxygen limitation than S. cerevisiae.

The adhesiveness of 2 unencapsulated nonfimbriated strains of Haemophilus influenzae, 23459 and 23330, and the encapsulated fimbriated strain 770235 to extracellular matrix (ECM) and to its isolated components was studied, as was the potential of H. influenzae plasminogen receptors to enhance degradation of ECM and bacterial penetration through basement membrane. All strains exhibited efficient adhesiveness to reconstituted basement membrane and to ECM from cultured human endothelial cells. Strains 23459 and 23330 efficiently adhered to immobilized laminin, fibronectin, and various collagens. Strain 770235 adhered efficiently to fibronectin and type I and III collagens and with low efficiency to laminin. With all 3 strains, plasmin generated on H. influenzae plasminogen receptors degraded laminin and fibronectin as well as ECM from human endothelial cells. Plasmin bound on H. influenzae cells also potentiated penetration of bacteria through a basement membrane preparation reconstituted on membrane filters. These results give evidence for a role of ECM adherence and plasminogen activation in the spread of H. influenzae through tissue barriers.

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Dekkera bruxellensis can outcompete Saccharomyces cerevisiae in environments with low sugar concentrations. It is usually regarded as a spoilage yeast but has lately been identified as an alternative ethanol production organism. In this study, global gene expression in the industrial isolate D. bruxellensis CBS 11270 under oxygen and glucose limitation was investigated by whole transcriptome sequencing using the AB SOLiD technology. Among other observations, we noted expression of respiratory complex I NADH-ubiquinone reductase although D. bruxellensis is a Crabtree positive yeast. The observed higher expression of NADH-generating enzymes compared to NAD+-generating enzymes might be the reason for the previously observed NADH imbalance and resulting Custer effect in D. bruxellensis. Low expression of genes involved in glycerol production is probably the molecular basis for high efficiency of D. bruxellensis metabolism under nutrient limitation. No D. bruxellensis homologs to the genes involved in the final reactions of glycerol biosynthesis were detected. A high number of expressed sugar transporter genes is consistent with the hypothesis that the competitiveness of D. bruxellensis is due to a higher affinity for the limiting substrate.

Aims:  Investigate the survival of liquid formulations of the biocontrol yeast Pichia anomala J121 at different temperatures, and develop a system for comparative studies of different storage conditions and formulations. Methods and Results:  The survival of P. anomala in liquid formulations with lactose, starch and trehalose amendments was measured during prolonged storage at temperatures ranging from −20 to +30°C. The relative survival of the stored cells was rapidly estimated by flow cytometry. After 4 weeks incubation at 4 and 10°C, 75–90% of the cells were viable, with no significant differences between the various formulations. Supplementing the storage buffer with lactose or trehalose increased the survival after longer incubations (8 and 12 weeks) at all temperatures (−20 to 30°C). Trehalose was the most effective protectant at 20 and 30°C (>20% viable cells after 12 weeks at 20°C). The biocontrol activity was maintained after formulation and prolonged storage of P. anomala. Conclusions:  The storage potential of liquid formulated P. anomala cells can be increased by supplementation with lactose or trehalose. The combination of a custom made incubation chamber and flow cytometry was suitable to evaluate stability of P. anomala formulations. Significance and Impact of the Study:  Liquid formulated P. anomala have a long shelf life. The developed test system can be used to study different formulations of other biocontrol agents.