Assessment of saccharification and fermentation of brown seaweeds to identify the seasonal effect on bioethanol production
- 325 Downloads
Brown seaweeds such as the kelps are attractive sources of biomass for bioethanol production, but fully optimised saccharification and fermentation conditions have yet to be established. To address this, various saccharification methods using dilute and concentrated acid and enzymes were trialled on three kelp species, Laminaria digitata, Laminaria hyperborea and Saccharina latissima, collected through a full seasonal cycle. Enzymatic hydrolysates were then fermented using Saccharomyces cerevisiae and Pichia angophorae to identify seasonal variations in ethanol yields. Highest glucose yields were achieved using concentrated acid, followed by enzymatic and dilute acid saccharification, respectively. The effect of seasonality showed that the highest glucose and ethanol yields were from kelps harvested during the autumn months and lowest during winter and spring months. However, the season at which biomass was collected did not have any measurable impact on the method of saccharification. Differences in ethanol yields between seaweed species were found with P. angophorae producing more ethanol from L. digitata and L. hyperborea hydrolysates, whilst S. cerevisiae was better for fermentation of S. latissima hydrolysates. It was observed that ethanol conversion yields with S. cerevisiae were higher than the theoretical maximum based on the yield of glucose identified, suggesting that other sugars in addition to glucose were co-fermented. For glucose liberation from seaweeds, terrestrial-derived cellulose and hemicellulose enzyme blends were suitable, but for liberation of all sugar monomers from seaweed polymers, other hydrolytic enzymes need to be investigated. In addition, fermentative microorganisms that are more tolerant of salinity and polyphenols are still required and ideally, be strains that can be engineered to ferment all carbohydrate sources present in kelps.
KeywordsBioethanol Macroalgae Seasonality Saccharification Saccharomyces cerevisiae Pichia angophorae
The authors acknowledge funding for the BioMara project (www.biomara.org) by the European Regional Development Fund through the INTERREG IVA Programme, Highlands and Islands Enterprise, The Crown Estate, Northern Ireland Executive, Scottish Government and Irish Government. The authors would also like to thank Fermentis, France, for kindly providing the Safdistil C70 strain and Novozymes, Denmark, for provision of the enzyme blends.
MS, DG and KB have made substantial contributions to conception and design, interpretation of data and revision of the manuscript and have given final approval of the version to be published.
- Annan W, Hirst E, Manners D (1965) 34. The constitution of laminarin. Part IV. The minor component sugars. J Chem Soc 220–226. doi: 10.1039/JR9650000220
- Badger P (2002) Ethanol from cellulose: a general review. In: Janick J, Whipkey A (eds) Trends in new crops and new uses. ASHS Press, Alexandria, pp 17–21Google Scholar
- Candra KP (2012) Study on bioethanol production using red seaweed Eucheuma cottonii from Bontang sea water. J Coastal Dev 15:45–50Google Scholar
- Chynoweth DP (2002) Review of biomethane from marine biomass. University of Florida, GainesvilleGoogle Scholar
- Khambhaty Y, Mody K, Gandhi MR, Thampy S, Maiti P, Brahmbhatt H, Eswaran K, Ghosh PK (2012) Kappaphycus alvarezii as a source of bioethanol. Bioresour Technol 103:180–185Google Scholar
- Kurtzman C, Fell JW, Boekhout T (2011) The yeasts: a taxonomic study. Elsevier, LondonGoogle Scholar
- Larsson S, Palmqvist E, Hahn-Hägerdal B, Tengborg C, Stenberg K, Zacchi G, Nilvebrant N-O (1999) The generation of fermentation inhibitors during dilute acid hydrolysis of softwood. Enzyme Microb Technol 24:151–159Google Scholar
- Lee K, Hong M, Jung S, Ha S, Yu BJ, Koo HM, Park SM, Seo JH, Kweon DH, Park JC, Jin YS (2011) Improved galactose fermentation of Saccharomyces cerevisiae through inverse metabolic engineering. Biotechnol Bioeng 108:621–631Google Scholar
- NPCS Board of Consultants and Engineers (2015) The complete book on biomass based products (biochemicals, biofuels, activated carbon). Asia Pacific Business Press Inc, DelhiGoogle Scholar
- Walker GM (2010) Bioethanol: science and technology of fuel alcohol., BookBoonGoogle Scholar
- Yazdani P, Karimi K, Taherzadeh MJ (2011) Improvement of enzymatic hydrolysis of a marine macro-alga by dilute acid hydrolysis pretreatment. In: World Renewable Energy Congress (Bioenergy Technology), 8–13 May. Linköping University, Sweden, pp 186–191Google Scholar
- Zvyagintseva TN, Shevchenko NM, Popivnich IB, Isakov VV, Scobun AS, Sundukova EV, Elyakova LA (1999) A new procedure for the separation of water-soluble polysaccharides from brown seaweeds. Carbohydr Res 322:32–39Google Scholar