Recycling of acid-pretreatment hydrolyzates of rice straw for high bioethanol production by S. cerevisiae and P. stipitis fermentation

ABSTRACT

The current study developed a strategy to recycle the acid-pretreated hydrolyzate for multiple pretreatments of rice straw to increase the soluble sugar content in the medium, thereby enhancing bioethanol conversion. This process recovered a maximum glucose concentration of 10.4 g/L and xylose: 44.5 g/L in the recycled acid-pretreated rice straw hydrolyzate obtained after the third pretreatment. This resulted in a 2.4-fold increase in glucose recovery and a 2.3-fold increase in xylose recovery compared to the initial pretreatment process. For both glucose and xylose conversion strategies, a co-culture of hexose fermenting S. cerevisiae and P. stipitis, capable of fermenting both pentose and hexoses was employed. The maximum bioethanol titer achieved from the co-culture of S. cerevisiae and P. stipitis was 11.29 g/L. However, applying a sequential culture approach of S. cerevisiae followed by P. stipitis with an intermediate heat inactivation at 50°C resulted in an improvement of bioethanol titer to 12.39 g/L with productivity of 0.258 g/L/h. This led to an improvement in 2.9-fold and 1.2-fold bioethanol titer in comparison to sole fermentation by S. cerevisiae and P. stipitis, respectively. The reuse of acid pretreated hydrolyzate for high recovery of soluble sugar and subsequent fermentation by sequential culture strategy can maximize lignocellulosic bioethanol production.

KEYWORDS:

• Pretreatment
• hemicellulosic hydrolyzate
• sequential fermentation
• bioethanol
• rice straw

Acknowledgements

The authors acknowledge the SERB-DST, India for providing funding and the Indian Institute of Technology Guwahati, India, for providing the necessary facilities to conduct this research.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Credit authorship statement

Suraj K. Panda: Formulation of Concept, experimentation, writing, and drafting the original manuscript.

Soumen K. Maiti: Supervision, concept formulation, writing, reviewing, and editing the manuscript.

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567036.2024.2380870.

Additional information

Funding

This work was supported by the SERB, India.

Notes on contributors

Suraj K. Panda

Suraj K. Panda is a PhD graduate student at Indian Institute of Technology Guwahati, specializing in bioprocess development for lignocellulose bioethanol production. His research focuses on optimizing fermentation processes to enhance bioethanol yield and efficiency.

Soumen K. Maiti

Soumen K. Maiti received the Ph.D. degree in Chemical Engineering from IIT Bombay, India. Currently, he is an Associate Professor at IIT Guwahati, India. His research interests include biochemical engineering, biofuels, and bioprocess modeling and optimization.