CONTINUOUS ALCOHOL/MALOLACTIC FERMENTATION OF GRAPE MUST IN A BIOREACTOR SYSTEM USING IMMOBILIZED CELLS

Three cultures immobilized by entrapping within alginate gel beads and packed in near-horizontal acrylic columns (15.0° angle) were used for alcohol/malolactic fermentation of grape must. Immobilized cells of Saccharomyces cerevisiae spp. chablis were placed in the 1st column, S. cerevisiae cells (an alcohol-sucrose-tolerant yeast) in the 2nd and the Lactobacillus delbrueckii cells in the 3rd column. Grape must with different levels of sugar(s), were each fed to the bioreactor columns at dilution rate of 0.74 h⁻¹ and recycled at 37.0C. The percent fermentation efficiency and yield using the 1st and 2nd columns for grape must containing 33.3% sugar(s) were 92.9 and 91.5%, respectively, and the wine had 15.5% alcohol after 23 cycles (∼ 50 h fermentation). The viability of the immobilized yeast cells in the alginate gel-bead was 84%± 4.0. Immobilized Lactobacillus delbrueckii cells were then added to the 3rd column (in series 37.0C) and the three cultures resulted in alcohol/malolactic fermentation of the grape must, evidenced by the high level of alcohol formed and simultaneous transformation of malic to lactic acid. Sensory evaluation of the wine scored high (7.8 ± 2.0 based on a value of 10.0) and indicated the potential of using multiple immobilized cells of two specific yeast cultures and a malolactic Lactobacillus for wine production.     

Dormancy in Seeds of Anona crassiflora Mart

The seeds of Anona crassiflora Mart., an important tree of theBrazilian cerrado, have been found to take about 8 months forgermination to commence, and some 35-70 d more to achieve itfully; such seeds must remain in moist ground all this time.A poorly developed embryo, little more than a hyaline mass ofcells, was all that could account for the delayed germination.Inhibition by extracts of seed parts was negligible. In A. crassifloraafter-ripening is related more to morphological changes in theembryo than to chemical changes. As the seed cannot endure evena brief sojourn in dry soil, vegetative reproduction is themeans by which the tree spreads into new areas.     

Genetic Variability ofLepidium meyeniiand other AndeanLepidiumSpecies (Brassicaceae) Assessed by Molecular Markers

A phylogenetic survey based on similarity levels was performedfor 29 cultivated accessions of maca (Lepidium meyeniiWalp.)and 27 accessions of wild species ofLepidiumfrom Ecuador, Peruand Bolivia, with RAPD markers. Chromosome counts for each accessionwere also performed. The similarity tree matrix separated intwo main branches: cultivated and wild species. The similaritylevel among cultivated accessions was high (0.952 or higher)indicating a low level of polymorphism. Within the wild species,two main secondary branches could be resolved, of which onewas subdivided into two tertiary branches. Morphological evaluationof the wild species accessions within each main group identifiedthree wild species: (1)L. bipinnatifidum, consisting mostlyof tetraploids and a single octoploid accession; (2)L. kalenbornii,consisting only of tetraploid accessions; and (3)L. chichicara,consisting mostly of octoploid and a few tetraploid accessions.Clustering by principal coordinates analysis supported the resultsobtained by the similarity tree matrix. These results indicatethat none of the three wild species is related enough to beconsidered ancestral to the cultivatedL. meyenii. Three accessionsof intermediate position may be of hybrid origin. None of thewild species was found to be diploid, which suggests that polyploidyhas been an important adaptation to high altitude habitats inthese species.Copyright 1998 Annals of Botany Company Lepidum meyenii, Lepidium peruvianum, maca, DNA markers, phylogeny.     

Ant body posture: gaster curling increases ant speed

1. Body postures adopted by an animal can serve behavioural functions, homeostasis, or energy balance. 2. We investigated the function of holding the gaster curled forward under the thorax in acacia ants, Pseudomyrmex spinicola Emery, by testing whether ants adopted this posture for defence, thermoregulation, or for efficient locomotion. 3. For the defence hypothesis, we expected an increase in the proportion of ants with curled gasters after a visual threat, a vibrational disturbance of a branch, or the release of nestmate's alarm pheromones. Our data did not support these predictions. 4. For the thermoregulation hypothesis, we found a positive correlation between temperature and proportion of curled‐gaster ants. However, we did not find a reduction in the proportion of curled‐gaster ants after shading them, as predicted by this hypothesis. 5. Our data supported the locomotion hypothesis: curled‐gaster ants walked 1 cm s^?1 faster than ants with the gaster held straight. Straight‐gaster ants walked with the thorax closer to the surface, a posture that likely shifts the centre of gravity closer to the surface in a manner similar to gaster curling. 6. Studying the role of the body posture in acacia ants and other insects will provide a better understanding of the kinematics of walking in challenging angles with respect to gravity.