Fermentation Study on Macroalgae Eucheuma cottonii for Bioethanol Production via Varying Acid Hydrolysis

Rachel Fran Mansa, Wei-Fang Chen, Siau-Jen Yeo, Yan-Yan Farm, Hafeza Abu Bakar, and Coswald Stephen Sipaut

Abstract The depletion of fossil fuel and the increase of human population lead to the search for more sustainable alternatives. Currently, bioethanol is produced from land-based crops, but in the future, marine biomass could be used as an alternative biomass source because it does not take up land area for cultivation. In this chapter, seaweed Eucheuma cottonii (cultivated in Sabah, Malaysia) was tested for its poten­tial for bioethanol production via fermentation by yeast Saccharomyces cerevisiae. E. cottonii contains cellulose and carrageenan which will be hydrolysed into glu­cose and galactose, which in turn was converted to ethanol by the yeast. This study showed that the extracted seaweed gives higher percentage of ethanol (9.6% v/v) compared to non-extracted seaweed. Subsequently, it was found that low molarity and high-temperature acid hydrolysis at 0.0 M, 100% (8.4% v/v) produced the most ethanol. It was followed by hydrolysis 0.1 M, 30% (7.7% v/v); 0.4 M, 30% (4.7% v/v); and 0.4 M, 100% (3.4% v/v) with fresh feedstock. In this research, among the three fermentation media, it was found that Yeast Peptone Dextrose (YPD) broth yields the highest percentage of ethanol (9.6% v/v) followed by Yeast Extract Peptone (YP) broth producing 4.7% v/v ethanol. This productivity level makes macroalgae a promising substrate for bioethanol production.

Keywords Eucheuma cottonii • Bioethanol • Fermentation • Acid hydrolysis • Extraction • Fermentation media

R. F. Mansa (*) • W.-F. Chen • S.-J. Yeo • Y.-Y. Farm • H. A. Bakar • C. S. Sipaut Energy and Materials Research Group, Materials and Minerals Research Unit, School of Engineering and Information Technology, Universiti Malaysia Sabah, Jalan UMS 88400, Kota Kinabalu, Sabah, Malaysia e-mail: rfmansa@ums. edu. my

R. Pogaku and R. Hj. Sarbatly (eds.), Advances in Biofuels, 219

DOI 10.1007/978-1-4614-6249-1_13, © Springer Science+Business Media New York 2013

13.1 Introduction

Bioethanol (ethyl alcohol, grain alcohol, CH3-CH2-OH or ETOH) is produced from biomass by the fermentation of available carbohydrates, usually simple sugars, into bioethanol and carbon dioxide, via the following chemical process (Harun et al. 2010):

image109(13.1)

Sabah has numerous species of seaweeds. Among these species, Eucheuma spp. is one of the most abundant species along the coastal area. The seaweeds cultiva­tion industry is growing from less than 5,000 tonnes in the year 1985 to more than 110,000 tonnes in the year 2005. The main producers are the Philippines, China, Indonesia, Malaysia (Sabah), Tanzania and Kiribati (Goh and Lee 2010). Seaweeds have different life cycle from terrestrial plants. The rapid growth of macroalgae offers vast harvesting amount in a single planting. They are more productive than other crops as more than five harvests can be obtained in a year. The ability to obtain numerous harvests from a single planting significantly reduces average annual costs for establishing and managing seaweeds, particularly in comparison to conventional crops. In addition, seaweeds flourish in salty water with sunlight and some simple nutrients from seawater. They do not need any chemical fertilisers. Large amount of energy and money is saved from fertilisation. This characteristic improves the sustainability of macroalgae-based third-generation biofuels. In gen­eral, seaweeds can be adapted to live in a variety of environmental conditions.

The potential of macroalgae as fermentation feedstock depends on its carbohy­drate and cellulose. These are the potential fermentation material for ethanol production. Table 13.1 shows the nutrition content of Eucheuma cottonii. Other than carbohydrate, small amounts of cellulose were also detected in the biomass. Fibrous content of E. cottonii can also be broken down to glucose by hydrolysis. Fibrous content includes crude fibre, soluble fibre, insoluble fibre, and total dietary fibre. This accounts for the major part of the seaweed.

Подпись:

image111 Подпись: 9.76 ± 1.33 1.10 ± 0.05 46.19 ± 0.42 5.91 ± 1.21 26.49 ± 3.01 10.55 ± 1.60 18.25 ± 0.93 6.8 ± 0.06 25.05 ± 0.99

Eucheuma cottonii

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