biotransformation of 5-hydroxymethylfurfural (hmf) by scheffersomyces stipitis during ethanol...

Biotransformation of 5-hydroxymethylfurfural (HMF) by Scheffersomyces stipitis during ethanol fermentation of hydrolysate of the seaweed Gelidium amansii Chae Hun Ra a , Gwi-Taek Jeong a , Myung Kyo Shin b , Sung-Koo Kim a,⇑ a Department of Biotechnology, Pukyong National University, Busan 608-737, Republic of Korea b Biolsystems Co. Ltd., Gwan-ri 430, Doyang-eub, Goheung-gun, Jeonnam, Republic of Korea highlights Thermal acid hydrolysis and enzymatic saccharification resulted in 43.5 g/L sugars. Ethanol concentration of 20.5 g/L was obtained using S. stipitis KCTC 7228. Glucose uptake increased at HMF concentrations <5 g/L in the fermentation medium. HMF was converted to 2,5-bis-hydroxymethylfuran by S. stipitis KCTC 7228. article info Article history: Received 31 January 2013 Received in revised form 29 April 2013 Accepted 29 April 2013 Available online 9 May 2013 Keywords: Ethanol fermentation HMF Biotransformation Gelidium amansii Scheffersomyces stipitis abstract The seaweed, Gelidium amansii, was fermented to produce bioethanol. Optimal pretreatment condition was determined as 94 mM H 2 SO 4 and 10% (w/v) seaweed slurry at 121 °C for 60 min. The mono sugars of 43.5 g/L with 57.4% of conversion from total carbohydrate of 75.8 g/L with G. amansii slurry 100 g dcw/L were obtained by thermal acid hydrolysis pretreatment and enzymatic saccharification. G. amansii hydrolysate was used as the substrate for ethanol production by separate hydrolysis and fermentation (SHF). The ethanol concentration of 20.5 g/L was produced by Scheffersomyces stipitis KCTC 7228. The effect of HMF on ethanol production by S. stipitis KCTC 7228 was evaluated and 5-hydroxymethylfurfural (HMF) was converted to 2,5-bis-hydroxymethylfuran. The accumulated 2,5-bis-hydroxymethylfuran in the medium did not affect galactose and glucose uptakes and ethanol production. Biotransformation of HMF to less inhibitory compounds by S. stipitis KCTC 7228 could enhance overall fermentation yields of seaweed hydrolysates to ethanol. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Marine macroalgae (seaweed) has emerged as an alternative and promising feedstock to produce a myriad of renewable fuels (Park et al., 2012). Use of seaweed as an energy feedstock for production of biodiesel, bioethanol, biogas, and biohydrogen has been investigated (Adams et al., 2009; Østgaard et al., 1993). Seaweed has a faster growth rate, lower land usage, higher CO 2 absorption and uptake rate, no need for fertilizers and no competition for food or freshwater resources compared to lignocellulosic biomass, (Singh et al., 2011). The red seaweed Gelidium amansii has a high content of easily degradable carbohydrates, making it a potential substrate for the production of liquid fuels. The carbohydrates in red seaweed comprise a neutral polymer (agarose) and a sulfate polysaccharide (agaropectin). Therefore, galactose and glucose are obtained by agarose and agaropectin hydrolysis (Park et al., 2012). Various pretreatment techniques have been introduced to enhance the overall hydrolysis yield, and can be categorized into physical, chemical, biological, enzymatic or a combination (Agbor et al., 2011). Dilute acid hydrolysis is commonly used to prepare seaweed hydrolysates for enzymatic saccharification and fermentation for economic reasons. However, the red seaweed G. amansii contains numerous inhibitory compounds, such as 5-hydroxymethylfurfural (HMF), which are generated by thermal acid hydrolysis pretreatment. Furfural is derived from the dehydration of pentose and HMF is formed from the dehydration of hexoses during sugar degradation by thermal acid (Boopathy et al., 1993; Lars- son et al., 1999). These compounds damage microorganisms by reducing enzymatic and biological activities, breaking down DNA, and inhibiting protein and RNA synthesis (Modig et al., 2002; San- chez and Bautista, 1998). Additional treatments are needed to solve the problems repre- sented by these inhibitory compounds and to facilitate the 0960-8524/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2013.04.122 ⇑ Corresponding author. Tel.: +82 52 629 5868; fax: + 82 51 629 5863. E-mail address: [email protected] (S.-K. Kim). Bioresource Technology 140 (2013) 421–425 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech

biotransformation of 5-hydroxymethylfurfural (hmf) by scheffersomyces stipitis during ethanol...

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