Influence of fermentation on the characteristics of Baltic Sea macroalgae, including microbial profile and trace element content

Abstract

The aim of this study was to evaluate the possibility of fermenting Baltic Sea macroalgae (Ulva intestinalis, Cladophora rupestris, and Furcellaria lumbricalis) using Lactobacillus plantarum strain LUHS135, which possesses antimicrobial properties, without additional pre-treatment with a fermentable substrate. To evaluate the effectiveness of the treatment, analysis of the microbial profile, antimicrobial and antioxidant characteristics, and trace element concentrations was performed. Fermentation with strain LUHS135 reduced the pH of C. rupestris < 4.5; however, that of U. intestinalis and F. lumbricalis remained unchanged after 12 h of fermentation. Metagenomic analysis showed that the algae can be contaminated with potentially harmful microorganisms which remain after fermentation despite the use of a technological microorganism possessing antimicrobial properties. However, the synergic mechanism of the algae and LUHS135 combination showed a broader spectrum of pathogen inhibition. Also, the health claims associated with algal products must be based on sufficient evidence of algal chemical safety indicators, for which heavy metals (especially lead and arsenic) are very important. Finally, the use of fermentable sugars (to reduce the pH of fermented samples and to prolong shelf life) and application of ultrasound treatment before fermentation could be further tested as a pre-pre-treatment method to control the fermentation process. Also, preparation of extracts of the antimicrobial compounds could be a possible way of reducing heavy metal concentrations and of using this prospective raw material at industrial scale.