Presentation Information
[P02-215]Expanding the Substrate Utilization Range of Sulfolobus acidocaldarius: From Hemicellulose to Cellulose
○Areum Lee1, Jaeho Cha2,3, Hyeoncheol Francis Son1,4,5 (1. School of Biological Sciences and Technology, Chonnam National University, Gwangju 61186 (Korea), 2. Microbiological Resource Research Institute, Pusan National University, Busan 46241 (Korea), 3. Department of Microbiology, College of Natural Science, Pusan National University, Busan 46241 (Korea), 4. Institute of Synthetic Biology for Carbon Neutralization, Chonnam National University, Gwangju 61186 (Korea), 5. Institute of Systems Biology and Life Science Informatics, Chonnam National University, Gwangju 61186 (Korea))
Keywords:
Lignocellulosic biomass,Sulfolobus acidocaldarius,Cellulose utilization,Cellulase engineering,Carbohydrate-binding module (CBM)
[Purpose]
Lignocellulosic biomass is an abundant and renewable carbon source composed primarily of cellulose and hemicellulose; however, its efficient microbial conversion remains challenging due to the structural recalcitrance of cellulose and the heterogeneous nature of hemicellulose. Sulfolobus acidocaldarius, a thermoacidophilic archaeon, is a promising host for industrial bioprocesses as it grows optimally under high-temperature and low-pH conditions. Although it can utilize a broad spectrum of sugars, including glucose, xylose, and arabinose derived from hemicellulose, the absence of endogenous enzymes required for polymer depolymerization prevents direct utilization of cellulose and hemicellulose. This study aims to expand substrate utilization of S. acidocaldarius from hemicellulose toward cellulose.
[Method]
To enable hemicellulose utilization, S. acidocaldarius was engineered by introducing heterologous enzymes involved in hemicellulose depolymerization. To extend substrate utilization to cellulose, cellulase engineering strategies are being developed, including fusion with carbohydrate-binding modules (CBMs) to enhance substrate binding and accessibility. CBM candidates were identified through sequence similarity network (SSN) analysis, and fusion constructs are currently being expressed in Escherichia coli. In parallel, transporter systems are being investigated to improve the uptake of sugars derived from cellulose hydrolysis.
[Results]
The engineered strain exhibited improved growth on hemicellulosic substrates, demonstrating successful implementation of hemicellulose utilization. In addition, the introduced cellulase showed sufficient enzymatic activity toward soluble cellulose derivatives such as carboxymethyl cellulose (CMC). However, this activity did not translate into effective cellular growth when cellulose was provided as a carbon source.
[Consideration]
These findings indicate that enzymatic activity alone is insufficient for efficient cellulose assimilation. Additional limitations, including inefficient uptake of hydrolysis products and limited accessibility to insoluble crystalline cellulose, are likely contributing factors.
[Conclusion]
Ongoing efforts, including CBM-based cellulase engineering and transporter identification, are expected to improve cellulose utilization. This work represents a step toward developing an engineered S. acidocaldarius strain capable of utilizing both hemicellulose and cellulose and establishing a thermoacidophilic platform for efficient lignocellulosic biomass conversion.
Lignocellulosic biomass is an abundant and renewable carbon source composed primarily of cellulose and hemicellulose; however, its efficient microbial conversion remains challenging due to the structural recalcitrance of cellulose and the heterogeneous nature of hemicellulose. Sulfolobus acidocaldarius, a thermoacidophilic archaeon, is a promising host for industrial bioprocesses as it grows optimally under high-temperature and low-pH conditions. Although it can utilize a broad spectrum of sugars, including glucose, xylose, and arabinose derived from hemicellulose, the absence of endogenous enzymes required for polymer depolymerization prevents direct utilization of cellulose and hemicellulose. This study aims to expand substrate utilization of S. acidocaldarius from hemicellulose toward cellulose.
[Method]
To enable hemicellulose utilization, S. acidocaldarius was engineered by introducing heterologous enzymes involved in hemicellulose depolymerization. To extend substrate utilization to cellulose, cellulase engineering strategies are being developed, including fusion with carbohydrate-binding modules (CBMs) to enhance substrate binding and accessibility. CBM candidates were identified through sequence similarity network (SSN) analysis, and fusion constructs are currently being expressed in Escherichia coli. In parallel, transporter systems are being investigated to improve the uptake of sugars derived from cellulose hydrolysis.
[Results]
The engineered strain exhibited improved growth on hemicellulosic substrates, demonstrating successful implementation of hemicellulose utilization. In addition, the introduced cellulase showed sufficient enzymatic activity toward soluble cellulose derivatives such as carboxymethyl cellulose (CMC). However, this activity did not translate into effective cellular growth when cellulose was provided as a carbon source.
[Consideration]
These findings indicate that enzymatic activity alone is insufficient for efficient cellulose assimilation. Additional limitations, including inefficient uptake of hydrolysis products and limited accessibility to insoluble crystalline cellulose, are likely contributing factors.
[Conclusion]
Ongoing efforts, including CBM-based cellulase engineering and transporter identification, are expected to improve cellulose utilization. This work represents a step toward developing an engineered S. acidocaldarius strain capable of utilizing both hemicellulose and cellulose and establishing a thermoacidophilic platform for efficient lignocellulosic biomass conversion.
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