{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T06:07:25Z","timestamp":1789106845424,"version":"build-2803163510"},"reference-count":50,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T00:00:00Z","timestamp":1789084800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Microbiol."],"abstract":"<jats:p>\n                    The acid-tolerant yeast\n                    <jats:italic>Issatchenkia orientalis<\/jats:italic>\n                    is a promising platform for the sustainable production of organic acids. However, the inefficient conversion of lignocellulosic biomass-derived sugars, primarily due to carbon catabolite repression (CCR), reduces overall production efficiency and limits its industrial application. In this study, we established a targeted genetic framework for efficient glucose\u2013xylose co-utilization by coordinating hexokinase (HXK) modulation and transport-level engineering. Sequential fed-batch fermentations revealed that a xylose-initiated feeding strategy achieved a 2.04-fold higher lactic acid yield than simultaneous fermentation. To bypass carbon catabolite repression, endogenous hexokinases were characterized, and single deletions (\n                    <jats:italic>hxk<\/jats:italic>\n                    1\u0394,\n                    <jats:italic>hxk<\/jats:italic>\n                    2\u0394, or\n                    <jats:italic>hxk<\/jats:italic>\n                    3\u0394) were conducted to attenuate glucose dominance. While this approach improved lactic acid yields, it simultaneously imposed severe kinetic bottlenecks. To address these limitations, heterologous sugar transporters, plant-derived\n                    <jats:italic>AtSWEET7<\/jats:italic>\n                    and yeast-derived\n                    <jats:italic>LST1<\/jats:italic>\n                    , were integrated. Characterization in the intact background revealed that the Major Facilitator Superfamily (MFS)-type\n                    <jats:italic>LST1<\/jats:italic>\n                    from\n                    <jats:italic>Lipomyces starkeyi<\/jats:italic>\n                    outperformed\n                    <jats:italic>AtSWEET7<\/jats:italic>\n                    . Double-copy integration of\n                    <jats:italic>LST1<\/jats:italic>\n                    yielded the engineered SD108XL-LST2 strain, which achieved a lactic acid titer of 53.4 g\/L within 56 h from a mixed-sugar substrate containing approximately 45 g\/L glucose and 44 g\/L xylose. Notably, the final yield (0.63 g\/g) and volumetric productivity (0.96 g\/L\u00b7h) represented 57.5% and 47.7% increases over the parental SD108XL strain, respectively. This transport-driven strategy effectively overrides native metabolic hierarchies while preserving essential glycolytic signaling, offering a robust framework for high-efficiency lignocellulosic biorefineries for organic acid production.\n                  <\/jats:p>","DOI":"10.3389\/fmicb.2026.1951033","type":"journal-article","created":{"date-parts":[[2026,9,11]],"date-time":"2026-09-11T05:29:13Z","timestamp":1789104553000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Engineering the acid-tolerant yeast Issatchenkia orientalis for efficient lactic acid production via optimized glucose and xylose utilization"],"prefix":"10.3389","volume":"17","author":[{"given":"Yejin","family":"Lin","sequence":"first","affiliation":[{"name":"Department of Chemical Engineering, College of Engineering, Kyung Hee University","place":["Yongin-si, Gyeonggi-do, Republic of Korea"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ayoung","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering, College of Engineering, Kyung Hee University","place":["Yongin-si, Gyeonggi-do, Republic of Korea"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daeun","family":"Lee","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering, College of Engineering, Kyung Hee University","place":["Yongin-si, Gyeonggi-do, Republic of Korea"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nam Kyu","family":"Kang","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering, College of Engineering, Kyung Hee University","place":["Yongin-si, Gyeonggi-do, Republic of Korea"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,9,11]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"547","DOI":"10.1016\/j.procbio.2014.01.030","article-title":"Deletion of the HXK2 gene in Saccharomyces cerevisiae enables mixed sugar fermentation of glucose and galactose in oxygen-limited conditions","volume":"49","author":"Bae","year":"2014","journal-title":"Process Biochem."},{"key":"B2","doi-asserted-by":"publisher","first-page":"foag035","DOI":"10.1093\/femsyr\/foag035","article-title":"Reprogramming a Hgt-family Kluyveromyces marxianus sugar transporter by site-directed mutagenesis to enable co-consumption of glucose and xylose","volume":"26","author":"Donzella","year":"2026","journal-title":"FEMS Yeast Res"},{"key":"B3","doi-asserted-by":"publisher","first-page":"543","DOI":"10.1146\/annurev-biochem-060815-014520","article-title":"Shared molecular mechanisms of membrane transporters","volume":"85","author":"Drew","year":"2016","journal-title":"Annu. 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