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In this study, mixed fruit peel waste was anaerobically fermented in a stirred-tank bioreactor using Wickerhamomyces sp. UFFS-CE-3.1.2 to produce organic acids and a multifunctional enzymatic bioproduct. During fermentation, sugars decreased from 6.51 to 0.22 g L\u22121, leading to the formation of citric acid (7.65 g L\u22121), ethanol (3.77 g L\u22121), glycerol (0.53 g L\u22121), and acetic acid (0.37 g L\u22121). The accumulation of organic acids likely imposed metabolic stress on the yeast, triggering physiological responses that mitigate oxidative stress. Consequently, the resulting enzymatic extract exhibited high lipase activity (185.63 U mL\u22121), late catalase induction (520.97 U mL\u22121), and stable superoxide dismutase activity (50 U mL\u22121). This enzymatic profile indicates the formation of a stress-adapted microbial system with potential applicability in processes involving lipid hydrolysis and oxidative mechanisms. The process was conducted without supplementation of synthetic medium and operated stably in a stirred-tank bioreactor. Overall, these results suggest a feasible microbial strategy for converting fruit waste into value-added bioproducts, contributing to the development of sustainable biotechnological processes.<\/jats:p>","DOI":"10.3390\/microorganisms14040907","type":"journal-article","created":{"date-parts":[[2026,4,17]],"date-time":"2026-04-17T10:11:04Z","timestamp":1776420664000},"page":"907","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Anaerobic Bioconversion of Mixed Fruit Waste into Organic Acids and a Multifunctional Enzymatic Bioproduct in a Stirred-Tank Bioreactor Using Wickerhamomyces sp. UFFS-CE-3.1.2"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-3594-6749","authenticated-orcid":false,"given":"Vit\u00f3ria Dassoler","family":"Longo","sequence":"first","affiliation":[{"name":"Laboratory of Microbiology and Bioprocess, Federal University of Fronteira Sul, Erechim 99700-000, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nair Mirely Freire Pinheiro","family":"Silveira","sequence":"additional","affiliation":[{"name":"Laboratory of Microbiology and Bioprocess, Federal University of Fronteira Sul, Erechim 99700-000, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5846-7047","authenticated-orcid":false,"given":"Marcelli Powzum","family":"Amorim","sequence":"additional","affiliation":[{"name":"Laboratory of Microbiology and Bioprocess, Federal University of Fronteira Sul, Erechim 99700-000, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-0302-3403","authenticated-orcid":false,"given":"Emanuely Fagundes da","family":"Silva","sequence":"additional","affiliation":[{"name":"Laboratory of Microbiology and Bioprocess, Federal University of Fronteira Sul, Erechim 99700-000, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Isabely Sandi","family":"Baldasso","sequence":"additional","affiliation":[{"name":"Laboratory of Microbiology and Bioprocess, Federal University of Fronteira Sul, Erechim 99700-000, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Arielle Cristina","family":"Fornari","sequence":"additional","affiliation":[{"name":"Laboratory of Microbiology and Bioprocess, Federal University of Fronteira Sul, Erechim 99700-000, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2548-9047","authenticated-orcid":false,"given":"Mateus Torres","family":"Nazari","sequence":"additional","affiliation":[{"name":"Graduate Program in Civil and Environmental Engineering (PPGEng), University of Passo Fundo (UPF), Passo Fundo 99052-900, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7787-971X","authenticated-orcid":false,"suffix":"Jr.","given":"S\u00e9rgio L.","family":"Alves","sequence":"additional","affiliation":[{"name":"Laboratory of Yeast Biochemistry, Federal University of Fronteira Sul, Chapec\u00f3 89815-899, SC, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3810-3000","authenticated-orcid":false,"given":"Helen","family":"Treichel","sequence":"additional","affiliation":[{"name":"Laboratory of Microbiology and Bioprocess, Federal University of Fronteira Sul, Erechim 99700-000, RS, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"172794","DOI":"10.1016\/j.scitotenv.2024.172794","article-title":"Municipal solid waste management challenges in developing regions: A comprehensive review and future perspectives for Asia and Africa","volume":"930","author":"Zhang","year":"2024","journal-title":"Sci. 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