ORIGINAL RESEARCH article

Front. Microbiol.

Sec. Microbiotechnology

Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1601691

This article is part of the Research TopicSynthetic Biology for Non-Model MicrobesView all 3 articles

Enhancing Lipid Production in Nannochloropsis salina via RNAi-Mediated Downregulation of Carbohydrate Biosynthesis

Provisionally accepted
HYUNGI  KOHHYUNGI KOH1Kyungmoon  ParkKyungmoon Park1See-Hyoung  ParkSee-Hyoung Park1Minsik  KimMinsik Kim2*Nam Kyu  KangNam Kyu Kang3*
  • 1Hongik University, Sejong, Republic of Korea
  • 2Inha University, Incheon, Republic of Korea
  • 3Kyung Hee University, Yongin, Republic of Korea

The final, formatted version of the article will be published soon.

Microalgae are promising platforms for sustainable biofuel production owing to their high photosynthetic efficiency and carbon fixation capacity. Nannochloropsis salina is particularly valued for its robust growth and lipid accumulation. However, redirecting carbon flux from carbohydrate to lipid biosynthesis remains a key challenge in microalgal metabolic engineering. In this study, RNA interference (RNAi) was employed to downregulate uridine diphosphate-glucose pyrophosphorylase (UGPase), a central enzyme in chrysolaminarin biosynthesis. After confirming the presence of core RNAi machinery (Argonaute, Dicer, and RDR) in N. salina, an RNAi construct targeting UGPase was introduced. Two transformants, NsRiUGPase 5 and NsRiUGPase 26, were selected through McrBC-PCR and qRT-PCR screening based on reduced methylation-sensitive PCR band intensity and UGPase transcript levels. These RNAi mutants exhibited significantly enhanced growth compared to wild-type. On day 12, dry cell weight (DCW) reached 4.77 g/L in NsRiUGPase 5 and 6.37 g/L in NsRiUGPase 26, representing 32.4% and 76.9% increases, respectively, compared to WT (3.60 g/L). Despite similar lipid contents per biomass, lipid productivity was markedly improved. On day 12, NsRiUGPase 26 achieved 196.3 mg/L/day, a 71.0% increase over WT (114.8 mg/L/day). Fatty acid methyl ester (FAME) analysis showed no significant difference in lipid composition among strains, indicating that UGPase knockdown did not affect lipid quality. These results demonstrate that RNAi-mediated suppression of UGPase successfully redirected carbon flux away from carbohydrate storage toward growth, thereby enhancing overall lipid productivity. This study provides new insights into carbon partitioning in N. salina and underscores RNAi as a powerful tool for microalgal biofuel optimization.

Keywords: Microalgae, Nannochloropsis salina, RNAi, UGPase, carbohydrate, Lipid

Received: 28 Mar 2025; Accepted: 30 Apr 2025.

Copyright: © 2025 KOH, Park, Park, Kim and Kang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Minsik Kim, Inha University, Incheon, 402-751, Republic of Korea
Nam Kyu Kang, Kyung Hee University, Yongin, Republic of Korea

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.