Two-Stage Cultivation of Anaerobic and Aerobic Bacteria : Exploring Novel Ways for the Utilization of Recalcitrant Aromatic Coumpounds
Ovaska, Henna (2025)
2025
Bioteknologian ja biolääketieteen tekniikan maisteriohjelma - Master's Programme in Biotechnology and Biomedical Engineering
Lääketieteen ja terveysteknologian tiedekunta - Faculty of Medicine and Health Technology
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Hyväksymispäivämäärä
2025-06-02
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202505306440
https://urn.fi/URN:NBN:fi:tuni-202505306440
Tiivistelmä
Lignin is a significant component of lignocellulosic biomass, but its complex and heterogeneous structure, composed of aromatic monolignol units (S-, G-, and H-lignin), makes its utilization challenging. One promising strategy for lignin upgrading involves the use of naturally lignin-degrading microbes. However, many of these microbes are unable to degrade all monolignol types or their intermediate degradation products, even if they can metabolize several individual compounds. Gallate is one such intermediate, utilized by only a few bacterial species, including both aerobic and anaerobic strains. Its aerobic conversion is hindered by its high susceptibility to oxidation under neutral or alkaline pH in the presence of oxygen. As a result, anaerobic conditions and fermentative anaerobic bacteria may offer a more suitable alternative for gallate conversion. Co-cultivation of anaerobic and aerobic bacteria could therefore enable the broader utilization of lignin-derived aromatic compounds and their intermediate degradation products without the need for extensive metabolic engineering.
The primary objective of this thesis was to establish a foundation for the two-stage cultivation of anaerobic and aerobic bacteria for the bioconversion of gallate. In this context, two-stage cultivation refers to a cultivation in which the metabolic product of one microbe serves as the substrate for another. Prior to the two-stage cultivation, growth conditions were optimized for both bacteria, and their growth metrics were evaluated. As a proof-of-concept, wax esters (WEs) were selected as the target product, synthesized by the aerobic bacterium Acinetobacter baylyi ADP1.
The two-stage cultivation was successfully implemented, resulting in WE production. This study further demonstrated that this approach can indirectly expand the range of lignin-derived compounds and their intermediate degradation products accessible to aerobic microbial metabolism. Notably, to the best of our knowledge, this is the first report of WE production from gallate. The successful implementation of this two-stage cultivation provides a foundation for enhancing WE yield and titer and for producing other value-added compounds from gallate.
The primary objective of this thesis was to establish a foundation for the two-stage cultivation of anaerobic and aerobic bacteria for the bioconversion of gallate. In this context, two-stage cultivation refers to a cultivation in which the metabolic product of one microbe serves as the substrate for another. Prior to the two-stage cultivation, growth conditions were optimized for both bacteria, and their growth metrics were evaluated. As a proof-of-concept, wax esters (WEs) were selected as the target product, synthesized by the aerobic bacterium Acinetobacter baylyi ADP1.
The two-stage cultivation was successfully implemented, resulting in WE production. This study further demonstrated that this approach can indirectly expand the range of lignin-derived compounds and their intermediate degradation products accessible to aerobic microbial metabolism. Notably, to the best of our knowledge, this is the first report of WE production from gallate. The successful implementation of this two-stage cultivation provides a foundation for enhancing WE yield and titer and for producing other value-added compounds from gallate.