A B S T R A C TThe aim of this study was to evaluate the probiotic potential of 16 yeast strains previously isolated during the natural fermentation of table olives Negrinha de Freixo cultivar, in relation to enzymatic activities; ability to grow at 37°C; antimicrobial activity; autoaggregation capacity; antioxidant activity and survival in gastrointestinal tract conditions. The highest antioxidant activity was observed for Saccharomyces cerevisiae, similar to the reference strain S. boulardii. Candida norvegica 7A and Galactomyces reessii 34A showed antifungal ability to the pathogenic microorganism Cryptococcus neoformans. Regarding the autoaggregation capacity, S. cerevisiae 15A, C. tropicalis 1A and C. norvegica 7A showed > 80% after 24 h. Pichia guilliermondii 25A and C. norvegica 7A were the most resistant to the simulated digestive conditions, similar to the reference strain (S. boulardii). Thus, these results suggest that some yeast strains involved in the fermentation of table olives have probiotic potential. Industrial relevance: In this study, we highlight the probiotic potential of yeast microbiota usually found in green table olives. These yeast strains could be used as culture starters for the development of new functional products.

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The vinegar is a millenary food, appreciated by consumers worldwide. The rice bran is a rice-processing by-product produced in a large scale, mainly employed in feed. This study describes a method for defatted rice bran (DRB) vinegar production by submerged fermentation, with optimized aeration and stirring conditions, evaluating its physico-chemical properties and acceptance. A 2 2 Full Factorial Design (FFD) was applied to evaluate the aeration (0.25-1.00 VVM) and stirring (100-500 rpm) effect on the stoichiometric yield (SY), total concentration of ethanol and acetic acid yield (TCY), and acetic acid productivity (AAP). SY ranged from 26.26 to 79.97%, TCY ranged from 78.04 to 100.50%, and AAP varied from 0.056 to 0.473 g L-1 h-1. The stirring had a positive effect in the SY and TCY, while both aeration and stirring had a positive effect in the AAP (p ≤ 0.05). The FFD allowed an acetic acid increase of ≅ 750 times under aeration of 1.00 VVM and stirring of 500 rpm, which made it possible to develop an industrially compatible method for vinegar production using DRB as substrate. Furthermore, DRB presents potential for vinegar production, with functional characteristics-including antioxidant activity-and sensorially accepted.

This bibliometric study explored the scientific publications of apple waste over the period from 2000 to 2020, aiming to contribute to the sustainable development of the apple industry toward waste-biorefinery implementation, advocating a circular economy. The bibliometric study covered the publications' evolution, research areas, top-cited papers, international collaborative networks, top countries and journals. The results demonstrate that 628 documents (604 articles and 24 reviews) studied apple waste over the last 20 years, and the number of publications exponentially increased after 2010. The most used keywords revealed that the main studied topics in the field were associated with technologies to manage apple pomace, the main solid waste generated from juice production, demonstrating a research trend toward renewable energy and bio-based products. The bibliometric study indicated that the most productive countries are China, India and the USA. Apple waste could be an environmentally friendly feedstock for biorefinery design and implementation. The biorefinery could produce value-added products (polyphenols, pectin, sugars and essential oils) and bioenergy (ethanol, methane, electricity and heat) in different industrial arrangements. The main technological routes described in the literature have been associated with the production of lactic acid, xylitol, ethanol, bioactive compounds, xyloglucan, films, pectin, acetic acid, acetone-butanol-ethanol, emulsifiers and inulinase enzyme. In conclusion, this review contributes to the decision-making for the industrial implementation of a waste biorefinery, advocating circular economy transition based on the sustainable valorization of apple waste.