Improvement of Enzymatic Hydrolysis of A Marine Macro-Alga by Dilute Acid Hydrolysis Pretreatment

Abstract

Abstract:The marine macro-alga Nizimuddinia zanardini was harvested from Persian Gulf to assess its biomass for fermentable sugar production. Hydrolysis of the macro-alga was investigated in two stages to evaluate the conversion of cellulose and hemicelluloses in biomass to corresponding monomeric sugars. The biomass was first subjected to dilute sulfuric acid pretreatments at 121 °C and then to enzymatic saccharification (45°C, pH 4.8) at different retention times. The results showed the ability of the first stage hydrolysis in depolymerization of xylan to xylose with a maximum yield of 64% (based on total xylose content) at 7% (w/w) acid concentration for 60 min. However, the yield of glucose from glucan was relatively low in the acid hydrolysis with a maximum of 14.4% (based on total glucan content) at 7% (w/w) acid concentration for 60 min. Under these conditions, no hydroxymethyl furfural (HMF) produced. Formation of furfural depended on the retention time and acid concentration, whereas the concentration of acetic acid was almost constant at retention times higher than 45 min and acid concentration of 7 %.The solid residuals were then subjected to enzymatic hydrolysis. The maximum yield of glucose from the macro-alga by enzymatic saccharification (45°C, pH 4.8, 24 h), using cellulase and β-glucosidase, was 70.2 g/kg (70.2% yield based on total glucan content).

Bioethanol Production from UK Seaweeds: Investigating Variable Pre-treatment and Enzyme Hydrolysis Parameters

“…This has often been investigated with different combinations of reaction times, temperatures and pressures as these parameters have shown to influence the maximum final yields of sugar that are liberated from the seaweed biomass [12,15,16]. Studies have also proved that a two stage process (an initial acid chemical pre-treatment followed by subsequent enzyme hydrolysis; similar to that commonly conducted for lignocellulosic biofuels) can increase the yields of fermentable sugars by at least double [17,18]. For example, Ra et al [19] added a blend of enzymes (Viscozyme-L and Celluclast; Novozymes, Denmark) for the hydrolysis of a pre-treated slurry of red algal species G. verrucosa, liberating 84.2% of the theoretical maximum of the species' total carbohydrate content [19].…”

Enhanced hydrolysis of Macrocystis pyrifera by integrated hydroxyl radicals and hot water pretreatment

“…Comparisons of the pretreatment temperature, time and hydrolysis condition of several macroalgae pretreatments process are provided in Table 4 (Lee et al, 2013;Borines et al, 2013;Yazdani et al, 2011). The results indicated that glucose yield from M. pyrifera after IHRHW pretreatment was much higher than that obtained after conventional pretreatments.…”

“…Glucan and xylan concentrations were calculated according to Eqs. (1) and (2), where the factors of 0.9 and 0.88 reflect the weight loss as a result of glucose-to-glucan and xylose-to-xylan conversion, respectively (Yazdani et al, 2011).…”

“…High amounts of furfural (0.2 g/100 g DM) were measured after acid and hydrothermal pretreatments (SchultzJensen et al, 2013). High amounts of furfural and formic acid were formed as a result of the acid pretreatment under 7% acid concentration or high temperature (180°C) condition (Lee et al, 2013;Yazdani et al, 2011),. The absence of inhibitors and high glucan and xylan recovery suggested that this IHRHW pretreatment technology can be applied to high-value macroalgae product isolation.…”

“…Several types of pretreatments have been performed on macroalgae, and glucose yield consequences have been estimated according to previous literature (Agbor et al, 2011). The chemical treatment most commonly used on macroalgae is acid pretreatment (Lee et al, 2013;Shi and He, 2008;Yazdani et al, 2011), thermal pretreatment and milling (Carlsson et al, 2012). All these pretreatment methods have the disadvantages of inhibitor formation, high energy consumption and environmental pollution.…”