Methodological tests of a heterotrophy index for aquatic ecosystems

Abstract

Experiments in glucose mineralization were carried out to investigate the effects caused by natural forcing functions on both the decomposition rates and heterotrophy capacity of aquatic ecosystems. In addition, the methodology used could show connections between mineralization rates measured in both laboratory and field work with those measured in aquatic ecosystems. Water samples from Infernão lagoon (21 degrees 35'S and 47 degrees 51'W) were collected, filtered, enriched with glucose, and incubated under aerobic and anaerobic conditions. The glucose concentration variation, dissolved oxygen (DO) consumption, pH, electric conductivity, and total CO2 amount in the water were determined for sixteen days. In the period with intense oxygen consumption there was also an evident glucose demand and the dissolved oxygen consumption rate was approximately the same as that for glucose mineralization. The process in the aerobic chambers was 2.2 times faster than that in the anaerobic chambers. An initial acidification of the water samples, probably due to microbial carbonic acid liberation, was noted. A rise in pH values was also observed at the end of the process. The electric conductivity was low for both aerobic and anaerobic chambers, indicating a probable ion uptake by microbial organisms due to the presence of carbon sources. The glucose content variations corresponded to both CO2 formation and dissolved oxygen consumption. It was estimated that 19.4% of the initial glucose content turned into CO2 and the remaining 80.6% into humic compounds and microbial biomass. This experiment showed that glucose can be used as a substrate indicating the heterotrophy of a given aquatic ecosystem.

Towards the Development of Electrical Biosensors Based on Nanostructured Porous Silicon

“…These results agree with previously reported measurements of electrical conductivity of glucose in water [17]. Moreover, the reduction in conductance is not attributed to water used for the dissolution of glucose, since water has been previously demonstrated to increase the conductivity of nanoPS [18,19].…”

Glucose uptake and extracellular polysaccharides (EPS) produced by bacterioplankton from an eutrophic tropical reservoir (Barra Bonita, SP–Brazil)

“…3). In earlier works (Antonio & Bianchini Jr., 2003;Panhota & Bianchini Jr., 2003), CO 2 derived from mineralization was the predominating product of decomposition.…”

“…2A). According to Antonio & Bianchini Jr. (2003) and Panhota & Bianchini Jr. (2003), glucose consumption by microorganisms includes basically the following competing processes: (i) biological assimilation (anabolic pathways); (ii) mineralization (catabolic routes) and (iii) reaction with other compounds, which results in formation of humic substances. By fitting the glucose decay data to a first-order kinetics model, we estimated a half-time of 6.9 days for glucose decomposition.…”

Evaluation of hollocelulase production by Lentinula edodes (Berk.) Pegler during the submerged fermentation growth using RSM

“…a studies it was found that there was in the culture media, a tendency to acidification during the first 48 hours, but in most of them, the pH stabilized or increased gradually. The low values are probably due to aerobic microbial activity (Antonio and Bianchini Junior, 2003). For further studies there must be tests using buffer or other residue that can simultaneously maintain the pH stabilization.…”