The WasteDigest project focuses on the valorization of agri-food waste, which is a rich source of bioactive compounds and offers a significant opportunity for sustainable resource management. 

The main objectives of the WasteDigest project are: a) characterization of phenolics in raw and valorized rosemary SW and the assessment of their in vitro/in vivo antioxidant activity; b) investigation of phenolic bioaccessibility during all phases of GI digestion; and c) monitoring phenolic biotransformation by analyzing microbial phenolic metabolites and short-chain fatty acids (SCFAs).

According to the objectives, the WasteDigest project is divided into three stages:

Stage 1: Valorization of rosemary SW and its impact on phenolic profile and their antioxidant activity

This stage focuses on enhancing the antioxidant activity and phenolic content of rosemary SWs through fermentation with Lactobacillus plantarum. The impact of valorization process (fermentation) will be evaluated by measuring antioxidant activity in vivo using S. cerevisiae as a model organism and in heterogeneous medium simulating food matrices. Furthermore, the targeted LC-MS/MS analysis to analyze phenolics content in raw and valorized rosemary SWs will be conducted. According to the results, the most abundant and bioactive phenolics will be selected to monitor their metabolites production during fecal fermentation (stage 3).

Objective 1: Characterize phenolics in raw and valorized rosemary SW and evaluate their in vitro and in vivo antioxidant activities. The screening will focus on compounds that dominate and express bioactive activities that could improve human health.

Hypothesis 1: Fermentation-based valorization of rosemary SW improves its phenolic profile and antioxidant activity.

Contribution to science: The findings will contribute to the development of sustainable valorization techniques for agri-food waste and highlight the potential of rosemary SW as a source of bioactive compounds for application in food industry.

Stage 2: Determination of phenolic bioaccessibility and antioxidant activity after GI digestion and fecal fermentation

Given that the final phase of digestion – fecal fermentation – is usually overlooked in studies, and to our knowledge, no research has analyzed the phenolic bioaccessibility of valorized agri-food waste materials throughout the entire digestion, this stage monitors the content of phenolics in raw and valorized rosemary SWs and investigates their bioaccessibility and antioxidant activity during GI digestion and fecal fermentation process.

Objective 2: Increase knowledge about the fate of selected phenolics during oral, gastro, intestinal and colon digestion phases by: (1) measuring the bioaccessibility of a selected phenolics present in raw and valorized rosemary SWs; and (2) assessing possible correlations between phenolic content of rosemary SWs and their in vivo/in vitro antioxidant activities after GI digestion and fecal fermentation.

Hypothesis 2: The bioaccessibility and antioxidant activity of phenolics in rosemary SWs are significantly affected by biotransformations occurring during specific phases of digestion.

Contribution to science: These findings will provide valuable insights into the bioaccessibility and in vivo/in vitro antioxidant activity of phenolics from raw and valorized rosemary SWs across different phases of digestion and fecal fermentation, improving understanding of the phenolic transformation processes.

Stage 3: Investigation of microbial metabolites during fecal fermentation

This stage focuses on advancing the understanding of the interactions between phenolics and the gut microbiota by evaluating the microbial metabolites produced during fecal fermentation (4 sampling time points). It builds on the findings of Stage 1 by analyzing the biotransformation of selected phenolics from raw and valorized rosemary SWs.

Objective 3: Determine the phenolic biotransformation during fecal fermentation by 1) monitoring phenolic microbial metabolites using target UHLC-MS/MS; 2) monitoring SCFAs production to evaluate the influence of rosemary SWs phenolics on microbial fermentation activity; 3) compering microbial phenolic metabolites from raw and valorized rosemary SWs.

Hypothesis 3: Valorized rosemary SW provide better substrate for fecal microbiota, resulting in greater production of microbial metabolites compared to raw rosemary SW.

Contribution to science: This stage will enhance understanding of the metabolic pathways involved in phenolic transformation by fecal microbiota.