A novel rice hull - microalgal biorefinery for the production of natural phenolic compounds comprising of rice hull acid pretreatment and a two-stage Botryococcus braunii cultivation process

Polytimi Papavasileiou; Stamatis Koutras; Eleni Koutra; Sameh S Ali; Michael Kornaros

doi:10.1016/j.biortech.2023.129621

A novel rice hull - microalgal biorefinery for the production of natural phenolic compounds comprising of rice hull acid pretreatment and a two-stage Botryococcus braunii cultivation process

Bioresour Technol. 2023 Nov:387:129621. doi: 10.1016/j.biortech.2023.129621. Epub 2023 Aug 5.

Authors

Polytimi Papavasileiou¹, Stamatis Koutras¹, Eleni Koutra¹, Sameh S Ali², Michael Kornaros³

Affiliations

¹ Laboratory of Biochemical Engineering and Environmental Technologies (LBEET), Department of Chemical Engineering, University of Patras, 26504 Patras, Greece; Institute of Circular Economy and Environment (ICEE), University of Patras' Research and Development Center, 26504 Patras, Greece.
² Botany Department, Faculty of Science, Tanta University, Tanta 31527, Egypt; Biofuels Institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China.
³ Laboratory of Biochemical Engineering and Environmental Technologies (LBEET), Department of Chemical Engineering, University of Patras, 26504 Patras, Greece; Institute of Circular Economy and Environment (ICEE), University of Patras' Research and Development Center, 26504 Patras, Greece. Electronic address: kornaros@chemeng.upatras.gr.

PMID: 37544534
DOI: 10.1016/j.biortech.2023.129621

Abstract

Recently, the rising demand of the industry for natural phenolic antioxidant compounds has turned to the study of microalgae as potential sources. Yet, more economic substrates for microalgal cultivation are sought to lower production costs. To this end, the present work deals with the utilization of rice hull hydrolysate (RHH) as substrate for microalgae Botryococcus braunii through a novel two-stage cultivation system. Initially, RHH was optimized to maximize the contained nutrients while minimizing its inhibitors content. The optimum point was reached under 121 °C, 60 min, 2% (v/v) H₂SO₄, 30% (w/v) loading. Next, B. braunii was successfully grown first heterotrophically in RHH (25%, v/v), obtaining high biomass production (6.67 g L^-1) and then autotrophically to enhance phenolics accumulation. At the end, a high phenolic content of 7.44 ± 0.60 mg Gallic Acid Equivalents g^-1 DW was achieved from the produced biomass, thus highlighting the potential of this novel biotechnological method.

Keywords: Acid pretreatment; Microalgae natural phenolic compounds; Rice hull biorefinery; Two-stage cultivation.

MeSH terms

Acids
Biomass
Biotechnology
Chlorophyta*
Microalgae*
Oryza*

Substances

Acids