In vitro study to evaluate the antimicrobial activity of various multifunctional cosmetic ingredients and chlorphenesin on bacterial species at risk in the cosmetic industry

Modeling bacterial interactions uncovers the importance of outliers in the coastal lignin-degrading consortium

Lignin, as the abundant carbon polymer, is essential for carbon cycle and biorefinery. Microorganisms interact to form communities for lignin biodegradation, yet it is a challenge to understand such complex interactions. Here, we develop a coastal lignin-degrading bacterial consortium (LD), through "top-down" enrichment. Sequencing and physiological analyses reveal that LD is dominated by the lignin degrader Pluralibacter gergoviae (>98%), with additional rare non-degraders. Interestingly, LD, cultured in lignin-MB medium, significantly enhances cell growth and lignin degradation as compared to P. gergoviae alone, implying a role of additional outliers. Using genome-scale metabolic models, metabolic profiling and culture experiments, modeling of inter-species interactions between P. gergoviae, Vibrio alginolyticus, Aeromonas hydrophila and Shewanella putrefaciens, unravels cross-feeding of amino acids, organic acids and alcohols between the degrader and non-degraders. Furthermore, the sub-population ratio is essential to enforce the synergy. Our study highlights the unrecognized role of outliers in lignin degradation.

Investigation of the constituents of commercially available toothpastes

OBJECTIVES

Toothpaste plays a pivotal role in oral and dental hygiene. This cross-sectional study not only investigates the constituents of toothpastes available in the market and their frequency across different brands but also delves into the potential side effects, irritations, or unfavourable outcomes of these constituents, emphasizing the broader health and environmental implications.

METHODS

The largest of the five major chain markets in each district of Istanbul was visited, and adult toothpastes were included in this study. All the constituents that make up the toothpaste were individually recorded in an Excel database. Subsequently, literature regarding the purposes, toxic and potential side effects of each ingredient was gathered using databases such as Google Scholar, PubMed and ScienceDirect. The percentages of these ingredients' occurrence among all the toothpastes were calculated, and the ingredients were categorized into 15 distinct groups based on their usage purposes.

RESULTS

There were 160 different varieties of toothpaste belonging to 19 different brands on the market shelves. Although a total of 244 different ingredients were identified, only 78 of them were included in the study. Among the analysed toothpaste types, 105 of them were found to contain 1450 ppm fluoride, whilst 26 toothpaste variants were discovered to have fluoride levels below this value. Among the various ingredients analysed, particular attention was drawn to commonly debated compounds in oral care products. Specifically, titanium dioxide was found in 68% (n = 111) of the varieties, sodium lauryl sulphate in 67% (n = 108) and paraben in 2% (n = 4), respectively.

CONCLUSION

Whilst certain ingredients may raise concerns for potential side effects and health considerations within the human body, the toothpaste has long been regarded as an indispensable tool for maintaining optimal oral and dental health. However, gaining a deeper understanding and conducting research on each constituent that comprises the toothpaste, as well as raising awareness in this regard, holds significant importance for human health.

Synergistic/antagonistic antimicrobial effects of cosmetic ingredients in combination with 1,2-hexanediol

With the rise of the clean beauty trend in the cosmetics and personal care industry, consumers' interest in cosmetic ingredients, especially preservatives, continues to grow. Paraben, previously the most used preservative in cosmetics, has been excluded from many products owing to its potential risks. Therefore, a movement to lower the content of various preservatives is ongoing. One approach to achieve a suitable level of preservation is to use multifunctional ingredients as preservative boosters. In this study, we aimed to confirm the synergistic antimicrobial interactions between various cosmetic ingredients and 1,2-hexanediol, a preservative introduced as a substitute for paraben, using the checkerboard assay. We also measured the antagonistic effect by measuring the fold changes in the minimum inhibitory concentration of 1,2-hexanediol. Niacinamide, a form of vitamin B3, showed synergistic antifungal activity with 1,2-hexanediol, which lowered the content of 1,2-hexanediol in the oil-solubilized toner formulation. Among the substances, 50000 ppm of methyl methacrylate crosspolymer elevated the minimum inhibitory concentration of 1,2-hexanediol against bacteria and fungi by 2‒8 times. Through this study, we suggest applying the synergistic effects of various cosmetic ingredients in the formulation as a method to effectively reduce the content of preservatives.