Yeasts in the traditional brewing of pito in Ghana

Yeasts from pito, a cereal-based traditional alcoholic beverage were isolated and characterized using biochemical and physiological tests. A total of 21 strains belonging to 8 genera were identified as Saccharomyces cerevisiae (8), Candida tropicalis (4), Kloeckera apiculata (2), Hansenula anomala (2), Torulaspora delbrueckii (3), Schizosaccharomyces pombe (1) and Kluvyeromyces africanus (1). Various diluents used for a 2 h holding period shows that 0.1% malt extract and peptone gave 20% decrease in cell viability for all the isolates, while phosphate buffer least supported the survival of the yeast cells with about 90% decrease in cell viability obtained for S. pombe at the end of the 2 h holding period. The effect of pH and temperature on the growth of the isolates revealed that at relatively low temperatures, growth increased with increasing pH, but a decrease was observed with increasing pH at high temperatures for S. cerevisiae and Candida tropicalis. All the isolates demonstrated good growth (10² to 10⁶ c.f.u./ml) at 10% ethanol concentration over a period of 8 days incubation. However, growth of K. africanus was completely inhibited after 4 days incubation period. The quality indices of the beverage produced using S. cerevisiae as a single-starter organism compared favourably with the traditional brew. The paper suggests ways of scientifically regulating the production of fermented foods in sub-Saharan Africa.     

Thidiazuron-induced plant regeneration from hypocotyl cultures of St. John's wort (Hypericum perforatum. cv 'Anthos')

 St. John's wort (Hypericum perforatum. cv 'Anthos') is a medicinal plant with evidence of efficacy as an anti-depressant. The present report describes the development of an in vitro regeneration system that utilizes thidiazuron [N-phenyl-N′-(1,2,3-thidiazol-yl)urea] for the induction of de novo shoots on etiolated hypocotyl segments of St. John's wort seedlings. The optimum level of thidiazuron supplementation to the culture medium was 5 μmol·l^–1 for a 9-day induction period followed by subculture of induced hypocotyl explants on basal medium. Other plant growth regulators including benzyladenine and indoleacetic acid were not effective in inducing regeneration on St. John's wort hypocotyls. Histological examination of the cultures revealed that the regenerated plants were derived from de novo developed shoots. Transfer of the regenerated shoots into a liquid medium with no plant growth regulators resulted in the rapid and prolific growth of viable plantlets. The rapid and efficient micropropagation system for St. John's wort may be useful for both the genetic improvement of this crop and the production of high-quality phytopharmaceutical preparations for the treatment of neurological disorders. Received: 19 March 1999 / Revision received: 5 July 1999 · Accepted: 17 August 1999     

Variation in the content of hypericins in four generations of seed progeny of <Emphasis Type="Italic">Hypericum perforatum</Emphasis> somaclones

The content of hypericins in in vitro regenerated Hypericum perforatum plants (R ₀) and four generations of their seed progeny (R ₁–R ₄) was compared. The mean content of hypericins in field-grown plants over the period 1992–2002 gradually increased under selection, and in the R ₄ generation it was almost seven-times higher than that in the R ₀ somaclones. Significant difference between hypericin content in diploids and tetraploids was detected in R ₀, R ₁ and R ₃ generations. Hypericin content in four diploid and tetraploid lineages originated from a single somaclone was genotype dependent. To eliminate the influence of environmental conditions during different growing seasons, we used seeds of selected R ₀–R ₃ plants to derive R′₁ to R′₄ generations cultivated during the same years. In this case no statistically significant difference in hypericin content was found between the R′₁–R′₄ generations. Apomictically and sexually derived plants were distinguished by PCR using variable numbers of tandem repeats (VNTR) primers. The content of hypericins in apomictically derived progenies was compared.     

Small‐scale resource tracking in a population of a long‐lived insect

How plant‐feeding insects distribute themselves and utilize their host plant resources is still poorly understood. Several processes may be involved, and their relative roles may vary with the spatial scale considered. Herein, we investigate small‐scale patterns, namely how population density of a gall midge is affected by individual growth form, phenology, and microsite characteristics of its herb host. The long‐lived plant individuals vary much with regard to number of shoots, flower abundance, and flowering phenology. This variation is connected to site characteristics, primarily the degree of sun exposure. The monophagous insect galls the flowers of the host plant – an easily defined food resource. It is a poor disperser, but very long‐lived; diapausing larvae can stay in the soil for many years. Galls were censused on individual plants during 5 years; from a peak to a low in gall population density. Only a very small fraction of the flowers produced (<0.5%) were galled even in the peak year. Nevertheless, most plant individuals had galls at least 1 year. In a stepwise multiple regression, plant size (number of shoots) was found to be the most important predictor of gall density (galls/flower). However, gall density decreased more than one order of magnitude over the plant size range observed. There was also a weak effect of plant phenology. Early flowering plants had lower gall densities than those starting later. Sun exposure had no direct effect on gall density, but a path analysis revealed indirect effects via the timing of flowering. Gall population change was highly synchronous in different parts of the study area with no significant decrease in synchrony with distance.     

Hyperforin: more than an antidepressant bioactive compound?

Hyperforin is a lipophilic compound that is present in great amounts in St. John's wort and that has been described as the main responsible for the antidepressant effects of this medicinal plant. In the last few years, evidence has accumulated pointing to other different effects of hyperforin with potential pharmacological interest. They include other neurological effects, effects on inflammation, as well as antibacterial, antitumoral and antiangiogenic effects.     

啤酒酵母对高浓麦汁的响应

综述了啤科高浓酿造中酵母对麦汁浓度、糖的种类、金属离子、应力、氧等因素的响应。     

Jasmonic acid-induced hypericin production in cell suspension cultures of Hypericum perforatum L. (St. John's wort)

Hypericum perforatum L. (St. John's wort) is an herbal remedy widely used in the treatment of mild to moderate depression. Hypericin, a photosensitive napthodianthrone, is believed to be the compound responsible for reversing the depression symptoms. In this study, novel in vitro cell culture systems of H. perforatum were used to monitor the effect of elicitation on cell growth and production of hypericin. A dramatic increase in cell growth and hypericin production was observed after exposure to jasmonic acid (JA). However, other elicitors such as salicylic acid (SA) and fungal cell wall elicitors failed to show any stimulatory effect on either cell growth or hypericin production. Cell cultures treated with JA and incubated in the dark showed increased growth and hypericin production as compared to the cultures grown under light conditions. Jasmonate induction in dark conditions played an important role in growth and hypericin production in cell suspension cultures, to our knowledge an undocumented observation.     

Extracts of St. John's wort and various constituents affect beta-adrenergic binding in rat frontal cortex

The present study was designed to get further insight into the mode of antidepressant action of extracts prepared from St. John's wort (SJW) and relevant active constituents. Down-regulation of central beta-adrenergic receptors (beta-AR's) has been widely considered a common biochemical marker of antidepressant efficacy. Although previous studies have reported a beta-AR down-regulation for SJW extracts, in vivo studies that compare the effects of SJW extracts with those of relevant active constituents on beta-AR density have not been done yet. We used quantitative radioligand receptor-binding-studies to examine in rats the effects of short-term (2 wks) and long-term (8 wks) administration of different SJW extracts and constituents on beta-AR binding in rat frontal cortex. The effects were compared to those of the standard antidepressants imipramine and fluoxetine. [125I]CYP binding to beta-AR was found to be decreased after short as well as after long-term treatment with imipramine (36%, 40%). Short-term treatment with fluoxetine decreased the number of beta-adrenergic receptors (17%) while long-term treatment with fluoxetine elicited an increase (14%) in beta-AR-binding. This effect was comparable to that of the lipophilic CO2 extract which decreased beta-AR-binding (13%) after two weeks and slightly increased the number of beta-AR's after 8 weeks (9%). Short-term treatment with the methanolic SJW extract decreased beta-AR-binding (14%), no effects for this extract were observed after 8 weeks. Treatment with hypericin led to a significant down-regulation (13%) of beta-AR's in the frontal cortex after 8-weeks, but not after 2 weeks, while hyperforin (used as trimethoxybenzoate, TMB), and hyperoside were ineffective in both treatment paradigms. Compared to the SJW extracts and single compounds the effect of imipramine on beta-AR-binding was more pronounced in both treatment paradigms.     

Biogeographic variation in genetic variability,apomixis expression and ploidy of St. John's wort (Hypericum perforatum) across its native and introduced range

Background and Aims

St. John''s wort (Hypericum perforatum) is becoming an important model plant system for investigations into ecology, reproductive biology and pharmacology. This study investigates biogeographic variation for population genetic structure and reproduction in its ancestral (European) and introduced (North America) ranges.

Methods

Over 2000 individuals from 43 localities were analysed for ploidy, microsatellite variation (19 loci) and reproduction (flow cytometric seed screen). Most individuals were tetraploid (93 %), while lower frequencies of hexaploid (6 %), diploid (<1 %) and triploid (<1 %) individuals were also identified.

Key Results

A flow cytometric analysis of 24 single seeds per individual, and five individuals per population demonstrated opposite patterns between ploidy types, with tetraploids producing more apomictic (73 %) than sexual (24 %) seed, while hexaploids produced more sexual (73 %) than apomictic (23 %) seed. As hexaploids are derived from tetraploids, these data imply that gene dosage, in addition to the effects of hybridization, influences the switch from apomictic to sexual reproduction. No significant differences in seed production were found between Europe and North America. An analysis of population structure based upon microsatellite profiling demonstrated three major genetic clusters in Europe, whose distribution was reflective of Pleistocene glaciation (e.g. refugia) and post-glacial recolonization of Europe.

Conclusions

The presence of pure and mixed populations representing all three genetic clusters in North America demonstrates that H. perforatum was introduced multiple times onto the continent, followed by gene flow between the different gene pools. Taken together, the data presented here suggest that plasticity in reproduction has no influence on the invasive potential of H. perforatum.