Effects of the water-soluble fraction of the mixture fuel oil/diesel on the microalgae Dunaliella tertiolecta through growth.

There is evidence that water-soluble fraction (WSF) from fuel oil/diesel mixture affects marine microbiota. In order to establish a sequence of WSF effects during microalgal growth, this work aimed to monitor Dunaliella tertiolecta exposed to WSF during 15 days. Three different pigments (chlorophyll a, lutein, and ß-carotene) and four metabolites (protein, lipids, fatty acids, and phenols) were studied, and FTIR spectroscopy was used to determine the biomolecular transitions of lipids and their accumulation. The results show that D. tertiolecta triggered a physiological and biochemical response with changes in growth rate, pigments, phenols, lipids, and proteins of the microalga, although fatty acid profile was unaltered. For all the biochemical parameters altered, there were significant differences with the controls. At the end of the assay, exposed D. tertiolecta showed similar values with the control on all the compounds analyzed, except lipids. FTIR absorbance showed an increase in unsaturated acyl chains within the exposed microalgae, giving support for a possible uptake of hydrocarbons from WSF. Variation in pigments and phenol contents is presented as an integrated antioxidant response to the stress imposed by WSF. Overall, this research provides information about the effects of WSF on D. tertiolecta, and the ability of this microalga to recover after long-term exposure to the water-soluble fraction of fuel oil/diesel.

Harvest time optimization leads to the production of native cassava starches with different properties.

The starch market is very diverse and demanding regarding the functional characteristics of the product. However, no technique based on the management of cassava root harvest time has been applied to obtain starches with different properties. Thus, in this study, cassava roots were harvested at different times and the structure and physicochemical properties of their starches were analyzed. Results indicated the time points in the first growth cycle of plants when all parameters associated with root growth were at their highest values. It was also observed that changes in the time of harvest leads to the production of starches with different granule size, crystallinity, and content of amylose and phosphorus, which resulted in changes in the thermal and pasting properties, as well as in the solubility of the starches and swelling power; that is, on the main determinant characteristics for applicability of the starches. Planned agricultural production monitoring, coupled with the analysis of the main starches characteristics for large-scale cassava crops, can provide commercial benefits for both farmers and industry, as it is possible to obtain starches with desired physicochemical characteristics for varied applications.

The long-term survival of Propionibacterium freudenreichii in a context of nutrient shortage.

AIMS: Propionibacterium freudenreichii is an actinobacterium widely used in dairy industry during the ripening process of Swiss-type cheeses and which presents probiotic properties. P. freudenreichii is reportedly a hardy bacterium, able to survive during the cheese-making process and when subjected to digestive stresses. During this study the long-term survival (LTS) of P. freudenreichii was investigated for 11 days by means of phenotypic characterization in a culture medium without the addition of any nutrients. METHODS AND RESULTS: For 11 days, in a non-nutrient supplemented culture medium, eight strains were monitored by measuring their optical density, counting colony-forming units (CFU) and using LIVE/DEAD staining and microscopy observation. Under these conditions, all strains displayed high survival rates in the culture medium, their culturability reaching more than 9 log10 CFU ml(-1) after 2 days. After 11 days, this value ranged from 7·8 to 8·2 log10 CFU ml(-1) depending on the strain, and at least 50% of the P. freudenreichii population displayed an intact envelope. As lysis of part of a bacterial population may be a microbial strategy to recover nutrients, in CIRM-BIA 138 (the strain with the highest population at day 11), cell lysis was assessed by quantifying intact bacterial cells using qPCR targeting the housekeeping gene tuf. No lysis was observed. CONCLUSION: Taken together, our results suggest that P. freudenreichii strains use a viable but nonculturable state to adapt to the LTS phase. SIGNIFICANCE AND IMPACT OF THE STUDY: Assessing the viability of P. freudenreichii and understanding their mechanisms for survival should be of great interest regarding their potential probiotic applications.