Microcalorimetric studies on the metabolism of Chlorella vulgaris

Microcalorimetric study of the growth of bacterial colonies of Lactococcus lactis IL1403 in agar gels

Growth of Lactococcus lactis IL1403 in solid agar gels and liquid cultures at different glucose concentrations of 2, 10 and 20 g/L and different inoculation rates from 10(0) to 10(6) cfu/mL with the 10-fold increment was studied using thermal activity monitor TAM III. In parallel to calorimetric measurements the changes of glucose and lactic acid concentrations and pH of culture media were measured in order to obtain additional information for the interpretation of calorimetric power-time curves. Maximal specific growth rates of heat evolution proportional to growth rates of biomass μ(max) (W/h), heat produced during different growth stages Q(TOT) (J/mL), Q(ExP) (J/mL) and duration of lag-phases λ (h) were obtained by processing calorimetric curves. The sizes of colonies were measured also at the end of growth using microscope. The data obtained together with calculated heat yield coefficient Y(Q) (J/cfu) allowed to analyze and describe quantitatively the growth of individual colonies and develop a model of multistage growth of a typical colony of L. lactis in 1% agar gel. Microcalorimetry used in combination with other relevant methods is a very powerful and precise tool in studying solid-state fermentations.

Antimicrobial properties of berberines alkaloids in Coptis chinensis Franch by microcalorimetry

The growth thermogenic curves of Escherichia coli (E. coli) affected by berberine, coptisine and palmatine were determined quantitatively by microcalorimetry. The power-time curves of E. coli with and without the three berberines alkaloids (BA) were acquired, meanwhile the extent and duration of inhibitory effects on the metabolism were evaluated by growth rate constant (k), half-inhibitory ratio (IC50), peak time of maximum heat-output power (tp), total heat-production (Qt) and so on. The inhibitory effects of BA on E. coli revealed that the sequence of their antimicrobial activity was berberine > coptisine > palmatine. The functional groups methylenedioxy at C2 and C3 on phenyl ring improve antimicrobial activity more remarkably than methoxyl at C2 and C3 on phenyl ring. However, the antimicrobial activity does not vary significantly with methylenedioxy or methoxyl at C9 and C10 on phenyl ring.

Microcalorimetric study on the growth and metabolism of microencapsulated microbial cell culture

The rate of heat output is one of the suitable measurements of metabolic activity of the organism or its parts, down to the cellular or even the sub-cellular levels. In this paper, microcalorimetry was first applied to study the metabolic activity of microbial in both alginate-polylysine-alginate and alginate-chitosan-alginate microencapsulated cultures as well as in free non-encapsulated culture. The organisms used for the measurements were Escherichia coli and Saccharomyces cerevisiae. As a result of this work, it was found that, despite E. coli cell in free non-encapsulated culture has the highest metabolic rate due to the highest value of heat output, the proliferation of the cells terminates quickly with a lowest biomass formed. And we found also an obviously longer stationary phase in microencapsulated culture. As far as S. cerevisiae was concerned, it was found that there was also the highest value of heat output in free non-encapsulated culture, but the cell density was lower than that in microencapsulated culture. On account of the microcalorimetric and metabolic measurements, it can be concluded that more substrate can be used to convert to biomass in microencapsulated culture which means a higher biomass yield existed.