Microwave Assisted Acid Hydrolysis of Brown Seaweed Ascophyllum nodosum for Bioethanol Production and Characterization of Alga Residue

Abstract

Brown&seaweed& Ascophyllum+nodosum++ Fast&microwave&assisted& hydrothermal&treatment Sugars Biochar Fermenta7on Ethanol ABSTRACT. For the first time, brown seaweed Ascophyllum nodosum was studied as a feedstock for the production of bioethanol. Saccharification was carried out by microwave assisted acid hydrolysis. The optimal condition was 0.4 M H 2 SO 4 , 3.13% (w/v) of biomass concentration, reaction temperature at 150 o C for 1 min, resulting in 127 mg/g monosaccharides of seaweed being released. The hydrolysates solution was concentrated and fermented directly without further detoxification. The concentration of furfural, hydroxymethyfufural and phenolicin the fermentation medium were 0.00 g/L, 0.01 g/L and 1.8 g/L, respectively. An ethanol concentration of 5.57 g/L and a conversion efficiency of 60.7% (based on glucose, galactose and mannose) were achieved. More than 50% energy yield of alga residue was recovered after hydrolysis, and the energy densification ranged from 1.4 to 1.7, with HHVs from about 19 -24 MJ/kg. The findings of this study demonstrated that microwave heating is a fast and efficient way to produce sugars and biochar in one simple process. And Ascophyllum nodosum can be potentially used as a feedstock for bioethanol and biochar production.

Microwave assisted step-by-step process for the production of fucoidan, alginate sodium, sugars and biochar from Ascophyllum nodosum through a biorefinery concept

“…The crude seaweed was analysed to determine moisture, protein, ash, lipid, phenolic and carbohydrate content as reported in our previous work (Yuan & Macquarrie, 2015a The sugar content was measured by phenol-H2SO4 method (Dubois et al, 1956) using fucose as the standard. …”

Lipid production through the single-step microwave hydrolysis of macroalgae using the oleaginous yeast Metschnikowia pulcherrima

“…Current research has developed techniques to enhance macroalgae valorisation through collaterally extracting proteins [1] and/or utilising other available saccharides, for instance through purification [12] or microbial processing [13][14][15][16][17][18]. Whilst the high carbohydrate, sulphur and nitrogen content make macroalgae a promising feedstock for microbial fermentation within a biorefinery setting, pretreatment and fermentation within such as process should be cost efficient and sustainable, utilising a microbe with versatile characteristics and ideally yield high-value products to enhance the feasibility of such a process.…”

“…Whilst the high carbohydrate, sulphur and nitrogen content make macroalgae a promising feedstock for microbial fermentation within a biorefinery setting, pretreatment and fermentation within such as process should be cost efficient and sustainable, utilising a microbe with versatile characteristics and ideally yield high-value products to enhance the feasibility of such a process. Recent research for microbial macroalgae utilisation focussed on ethanol [16], butanol [1] and biogas [15] production, with pretreatment often taking place via acid and/or enzymatic hydrolysis.…”

“…Considering the lack of lignin and the previous successful recovery of macroalgae constituents through microwave-assisted extraction [16,30], this technology offers a potentially viable alternative to produce an inexpensive microbial growth medium from macroalgae [16]. However, the thermochemical treatment of biomass generally produces mainly oligosaccharides and a range of inhibitors.…”

The application of microwave heating in bioenergy: A review on the microwave pre-treatment and upgrading technologies for biomass

“…At the time of writing, only one paper had been published which evaluated the HHV of brown seaweed Ascophyllum nodosum residue that was recovered after MW-assisted acid hydrolysis [92]. Although this work is traditionally classified as WT, it did however demonstrate that MW heating of seaweed with an additional acid catalyst can efficiently produce a liquid product stream rich in sugars and also a hydrochar residue with an energy yield of more than 50% in one process.…”