[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-271] Lactic acid production by Escherichia coli using chemically synthesized non-natural sugars

○Keisuke Hamaguchi¹, Hiroaki Nishijima¹, Hiro Tabata^1,2, Shuji Nakanishi¹ (1. Graduate School of Engineering Science, The University of Osaka (Japan), 2. Presidential Endowed Chair for "Platinum Society", The University of Tokyo (Japan))

Keywords:

Escherichia coli,Biorefinery,fermentation,sugar

Biotechnological production of value-added chemicals from biomass-derived sugars has attracted increasing attention as a key technology for realizing a carbon-neutral and sustainable society. However, the supply of biomass-derived sugars remains limited relative to the enormous demand for fuels and chemicals, and excessive industrial utilization may lead to competition with food resources. In addition, concerns have been raised regarding supply instability caused by climate change–induced yield losses and geopolitical risks. To address these challenges, our research group has been investigating rapid and stable sugar synthesis based on non-enzymatic chemical reactions. In this study, sugars were non-enzymatically synthesized via the formose reaction, in which various sugars are obtained from formaldehyde solution under alkaline conditions. Here, we evaluated the feasibility of bioprocesses utilizing the synthesized sugars enriched in non-natural components. Escherichia coli (E. coli) was employed as a model microorganism, and its growth behavior and fermentative production were examined using the synthesized sugars as the sole carbon source. No cell growth was observed in inorganic medium without substrate addition, whereas clear growth was observed when the synthesized sugars were supplied, indicating that E. coli can assimilate these sugars to support cell growth. Lactate production was not detected in the absence of a carbon source, while lactate accumulation was observed when the synthesized sugars were added. However, the overall carbon conversion toward lactate remained low under these conditions. To improve this conversion, we considered the role of intracellular redox balance in lactate formation. Since the reduction of pyruvate to lactate requires NADH, supplementation with an additional metabolizable sugar was expected to influence lactate production. Based on this idea, a small amount of glucose was co-supplied with the synthesized sugars. Co-feeding resulted in an increase in lactate production compared with single-substrate conditions. These observations suggest that glucose supplementation may have contributed to enhanced reducing power availability, thereby facilitating lactate formation from the synthesized sugars. Furthermore, fructose was examined as an alternative co-substrate. A similar tendency toward increased lactate production was observed when fructose was co-fed. Collectively, these findings indicate that supplementation with readily metabolizable sugars can enhance lactate production from the synthesized sugar mixtures. These results highlight the importance of intracellular redox balance in optimizing fermentative production from non-natural sugar substrates.