The MATH test. A three-phase assay?

This study aimed to investigating the possible interference caused by glass test tubes on the quantification of bacterial adhesion to hydrocarbons by the MATH test. The adhesion of four bacteria to hexadecane and to glass test tubes was evaluated employing different suspending polar phases. The role of the ionic strength of the polar phase regarding adhesion to glassware was investigated. Within the conditions studied, Gram-positive bacteria adhered to both the test tube and the hydrocarbon regardless of the polar phase employed; meanwhile, Escherichia coli ATCC 25922 did not attach to either one. The capacity of the studied microorganisms to adhere to glassware was associated with their electron-donor properties. The ionic strength of the suspending media altered the patterns of adhesion to glass in a strain-specific manner by defining the magnitude of electrostatic repulsion observed between bacteria and the glass surface. This research demonstrated that glass test tubes may interact with suspended bacterial cells during the MATH test under specific conditions, which may lead to overestimating the percentage of adhesion to hydrocarbons and, thus, to erroneous values of cell surface hydrophobicity.

Method-induced variation in the bacterial cell surface hydrophobicity MATH test.

Bacterial cell surface hydrophobicity is a relevant property in determining the ability of bacteria to adhere to inert surfaces. This property has been measured using the microbial adhesion to hydrocarbon (MATH) test. Several reports in the literature establish the percentage of adhesion to hydrocarbons (PoAtH) value produced by the MATH test for a broad variety of bacteria. Discrepancies in PoAtH values reported for the same strain of a specific microorganism suggest that some method-induced variation may exist, as different research teams employ different versions of the assay. The objective of the present study was to compare the performance of different versions of the MATH test as reported in the literature, to quantify the magnitude of the method-induced variation on PoAtH values. The study demonstrated that PoAtH values are influenced twice as much by variations in the employed assay than by actual differences in cell surface composition or architecture. The two L. reuteri strains studied responded differently to changes in assay conditions showing 40 and 70% method-dependent variation for strain ATCC 53609 and 55730, respectively. These results highlight the need to properly standardize the MATH test to enable comparison of PoAtH values produced by independent research teams.

Functionality of Agave Bagasse as Supplement for the Development of Prebiotics-Enriched Foods.

Agave bagasse is a fibrous-like material obtained during aguamiel extraction, which is also in contact with indigenous microbiota of agave plant during aguamiel fermentation. This plant is a well-known carrier of the prebiotic fructan-type carbohydrates, which have multiple ascribable health benefits. In the present work, the potential of ashen and green agave bagasse as functional ingredients in supplemented cookies was studied. For its application, the chemical, functional, properties of agave bagasses and formulated cookies were evaluated, as well as the physical properties of cookies. Chemical characterization was carried out by the proximate analysis of both bagasses and cookies, besides, the analysis of oligosaccharides was made by thin-layer chromatography and high-performance anion-exchange chromatography. In the same way, functional properties such as oil holding capacity, organic molecule absorption capacity, swelling capacity, and water holding capacity were analyzed in both agave bagasses and supplemented cookies. Finally, modifications in color and texture due to bagasse addition was studied through an analysis of total color difference and a penetrometric test, respectively. In this sense, ashen and green agave bagasses demonstrated chemical and functional properties for use in the food industry, since they increased oil holding capacity of cookies and transferred prebiotic fructooligosaccharides to both agave bagasse formulations, which remain active as a prebiotic ingredient in cookies after in vitro digestion and cookie manufacture, including thermal treatment. Hence, agave bagasse could be considered a valuable alternative for the addition of the nutritionally-relevant dietary fiber in healthier foods.