Recovery and upcycling of residual lactic acid and ammonium from biowaste into yeast single cell protein

Danfei Zeng, Song Wang, Yufeng Jiang, Yanyan Su, Yifeng Zhang*

*Corresponding author for this work

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Abstract

The yeast Saccharomyces cerevisiae is a potential candidate for converting waste resources into food-grade single cell protein (SCP). Food waste fermentation broth rich in lactic acid was tested as an alternative substrate source for S. cerevisiae in this study. An electrodialysis (ED) system was developed to recover lactate, acetate and ammonium ions (La-, Ac- and NH4+) from the broth. First, we evaluated the system resilience under various volatile fatty acids (VFAs) and pH levels. Initial acetate and lactate concentrations did not affect La- and Ac- recovery efficiencies but affected their ion fluxes and competitive ion transport. The migration of La- was delayed by increasing the initial acetate concentration, while Ac- migration was not affected by lactate concentrations. Increasing the broth pH reduced competitive H+ ions and thus improved the NH4+ recovery efficiency. Further, broth recirculation and pH control were examined to identify potential challenges associated with continuous flow in real-life applications. Recirculation caused a greater loss of recovered Ac- and NH4+ over the extended period. The pH control decreased VFAs recovery efficiencies because VFAs could not fully dissociate in the dilute, and more VFAs were lost in the concentrate. Finally, the recovery from lactate-rich fermentation broth was used as yeast substrate and contributed to a robust SCP yield of 0.62 g/g-C. Manufacturing one kilogram of SCP costs €6-10 in electricity and €3-6 in raw material. This study provides a better understanding of competitive ion transport during ED and uncovers potential biowaste resources for sustainable SCP production.
Original languageEnglish
Article number123632
JournalSeparation and Purification Technology
Volume314
Number of pages9
ISSN1383-5866
DOIs
Publication statusPublished - 2023

Bibliographical note

Danfei Zeng would like to acknowledge the China Scholarship Council for financial support. Yifeng Zhang thanks The Carlsberg Foundation (CF18-0084), The Ministry of Foreign Affairs of Denmark (No. 21-08-DTU), and Independent Research Fund Denmark (Project 1, No.171114) for funding the research.

Keywords

  • Single cell protein
  • Saccharomyces cerevisiae
  • Lactic acid fermentation
  • Electrodialysis
  • Food waste

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