Statistical Approach for Optimization of Ethanol Production from Fast-growing Trees: Acacia mangium and Acacia hybrid

Abstract

This is the first report of the potential of Acacia fast growing trees in Thailand, A. mangium and the Acacia hybrid (A. mangium x A. auriculiformis), as raw material for ethanol production through a simultaneous saccharification and fermentation process by Saccharomyces cerevisiae TISTR 5339. Alkaline pulping was applied as the pretreatment process. Optimization of ethanol production was studied using response surface methodology based on central composite design. The optimized conditions of 100 g/L solid loading and an A600 of S. cerevisiae TISTR 5339 of 2 gave observed values of ethanol production of 35.7 and 27.3 g/L, which corresponded with the predicted values of 32.32 and 26.37g/L from A. mangium and A. hybrid, respectively. This condition was then used for up-scaling in a 10-L stirred bioreactor. The improved maximum ethanol concentrations of 37.84 and 36.52 g/L were obtained from A. mangium and Acacia hybrid, respectively, within 96 h of cultivation at 30 °C and no aeration rate. Keywords INTRODUCTIONWith the depletion of the world's petroleum, alternative non-petroleum-based sources of energy are being looked at with greater interest. Many countries have begun focusing on renewable resources for production of ethanol-based fuels. Lignocellulosic biomass from woody plants has the potential to become a major source of fermentable sugars for the production of ethanol because trees are the most abundant source of biomass. Thus, lignocellulosic biomass has been considered a new resource for ethanol production.Because of its chemical composition, lignocellulosic biomass is very different from types of biomass that have large content of sugars or starch, as is customarily used in the biofuel industry. The structure of these former materials, mainly composed by cellulose, hemicellulose, and lignin, requires the process for biofuels production to be adjusted for each type of biomass, according to their component characteristics. Thus, pretreatment has been recognized as a necessary upstream process to improve the formation of sugars for downstream microbial and enzymatic processing.Different kind of pretreatment methods, under a large variety of conditions, have been studied to improve the fermentability and digestibility. Mechanical size reduction is a physical pretreatment to increase enzyme-accessible surface areas (Zhu et al. 2009). In addition to these other pretreatment options, steam explosion is a technique based on PEER-REVIEWED ARTICLE bioresources.com Boondaeng et al. (2015). "Ethanol from Acacia," BioResources 10(2), 3154-3168. 3155 subjecting the biomass to pressurized steam for a short duration of time and then suddenly depressurizing the system. Due to the explosive decomposition, the fibers are separated and changes to the microstructure are brought about by the suddenly reduced pressure (Brodeur et al. 2011). The treatments result in increasing cellulose digestibility of pretreated biomass and solubilizing a significant portion of the hemicellulosic component (Nibedita et al. 2012). To help wi...

THE PRESENCE OF BARK IN Acacia mangium WOOD IMPROVES ITS ENERGETIC POTENTIAL

“…As improvements, we can mention the increase in HHV (19.58 to 20.63 MJ kg -1 ) and the fixed carbon content (14.7 to 19.1%). This result may be related to the chemical composition of A. mangium bark, as demonstrated by Rosdiana et al (2017) and Vega et al (2019), with total extractives content in the order of 17-34%, higher than the extractives content found in the wood of this same specie, between 4-6% (BOONDAENG et al, 2015;VEGA et al, 2019). In its chemical composition, bark differs from wood by the presence of polyphenols and a higher percentage of extractives (ROSDIANA et al, 2017).…”

Fermentation Characteristics and Aromatic Profiles of Plum Wines Produced with Hanseniaspora thailandica Zal1 and Common Wine Yeasts

“…The ethanol concentration was analyzed using gas chromatography (Chromosorb-103, GC4000; GL Sciences; Tokyo, Japan) with an HP5 capillary (30 m × 0.32 mm × 0.25 µm; JW Scientific; Folsom, CA, USA) and FID detector under the following conditions: split flow, 50 mL/min; air flow, 250 mL/min; N2 carrier flow, 30 mL/min; column temperature, 185 °C; injector temperature, 250 °C; detector temperature, 250 °C. n-Propanol was used as the internal standard for comparison [ 42 ]. All measurements were performed in triplicate.…”

Ethanol production from cassava stem using Saccharomyces cerevisiae TISTR 5339 through simultaneous saccharification and fermentation

“…Aside from the cassava stem, other lignocellulose residues were also reported ( Table 3). The cellulose content from the cassava stem was compared to other reported cellulose content such as 44% for Acacia mangium and 42% for Acacia hybrid (Boondaeng et al, 2015), 26-43% for bamboo (Sánchez, 2009), 42-45% for corn cob (Kuhad and Singh, 1993;Prasad et al, 2007;Liu et al, 2010), 20-25% for hardwood (McKendry, 2002), 43% for the empty fruit bunch of oil palm (Garcia-Nunez et al, 2016), 28-36% for rice straw (Chen et al, 2008;Saini et al, 2015), 27-30% for softwood (McKendry, 2002), 42-48% for sugarcane bagasse (Kuhad and Singh, 1993;Rocha et al, 2015;Saini et al, 2015) and 5-34% for switch grass (Butkute et al, 2013;Saini et al, 2015). These figures indicated that cassava stem has a high potential to be used as a feedstock in bioconversion processes for ethanol fermentation, especially as it can be obtained in large quantities from local growers.…”

“…In the past decade, energy supply has been a primary concern as the global supply of petroleum is depleting (Owusu and Asumadu-Sarkodie, 2016). First generation biofuels that are made from starch, sugar and vegetable oil from crops, have raised some concerns regarding their economic benefits and the inability to produce adequate biofuels without threatening food supply (Boondaeng et al, 2015). As such, the search for new sources of biofuels has captivated global interest with lignocellulosic biomass-the most abundant feedstocks for a second generation biofuel -being of particular interest due to its low cost, as it can serve as an alternative to various raw materials such as agro-wastes, forestry wastes and pulp wastes (Saha, 2004;Talebnia et al, 2010;Chen, 2011;Singh and Bishnoi, 2012).…”