Statistical optimization of dilute acid pretreatment of lignocellulosic biomass by response surface methodology to obtain fermentable sugars for bioethanol production

Abstract

Central composite design to optimize sugar recovery from cotton straw and sunflower straw using dilute acid pretreatment was applied. Selected input variables were acid concentration, retention time, and temperature, as well as the response parameter of sugar yield. The optimum pretreatment conditions observed for maximum sugar yield are temperature: 121.7 C, acid concentration: 2.28% (vol/vol), and time: 36.82 minutes for cotton straw; temperature: 87.03 C, and acid concentration: 3.68% (vol/vol), and time: 36.82 minutes for sunflower straw.Maximum sugar concentrations were corresponded to 20 and 17.5 g L −1 under conditions for sunflower and cotton straw, respectively. This study not only investigates the sugar recovery efficiency statistically but also examines the ethanol production efficiency. As a result, the maximum ethanol concentration, ethanol yield, and ethanol productivity of 7.21 g L −1 , 0.41 g g −1 , and 0.10 g L −1 h −1 for cotton straw and 8.05 g L −1 , 0.40 g g −1 , and 0.11 g L −1 h −1 for sunflower straw were achieved via fermentation with Saccharomyces cerevisiae, respectively. The output of this study is important for the commercialization of bioprocesses that enable the conversion of the lignocellulosic waste matrix into high value-added products in a biorefinery concept.

Advances in Pretreatment of Straw Biomass for Sugar Production

“…Furthermore, a central composite design was used to enhance the sugar recovery efficiency and conversion of cotton and sunflower straw. Various parameters such as the acid concentration, reaction time, and temperature as well as the fermentable sugar yields were optimized, obtaining 20 and 15.5 g L −1 fermentable sugars from cotton (121.7°C, 2.28% acid concentration, 36.82 min) and sunflower straw (87.03°C, 3.68% acid concentration, 36.82 min) under optimum treatment parameters, respectively (Yildirim et al, 2021). Acid treatment has its advantages and disadvantages for the pretreatment of lignocellulosic feedstocks.…”

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“…Common lignocellulosic materials include agricultural wastes like straw and stover, food processing wastes like bagasse, brans, and pods, and dedicated energy crops like switchgrass and Miscanthus sp. These biomasses are composed structurally of hemicellulose, cellulose, and lignin bonded into a stiff matrix that resists hydrolysis into simple sugars and calls for pretreatment techniques (Malik et al, 2020;Yildirim et al, 2021). The African mesquite (Prosopis africana) tree is a perennial leguminous tree found throughout East and West Africa's savanna regions.…”

“…Physical pretreatment includes methods like microwave irradiation, ultrasound pretreatment, and size reduction operations. Ionic liquid delignification and acid or alkaline pretreatment are examples of chemical pretreatment methods, whereas CO2, SO2, or steam explosion and liquid hot water treatment are examples of physicochemical pretreatment methods (Karimi et al, 2013;Beig et al, 2021;Yildirim et al, 2021). The last pretreatment method is biological, which entails utilizing white-rot fungi and other microbes to break down the dense structure of lignocellulose while leaving the sugars, which can then be hydrolyzed and fermented.…”

Optimisation of dilute acid hydrolysis for bioethanol production from selected agricultural wastes

“…Fossil fuels are not environmentally friendly and cannot be replenished after they run out, therefore using them as a source of energy has continued to pose major environmental issues (Awoyale and Lokhat, 2021). Additionally, the high cost of producing petroleum products, the shrinking of the world's oil supplies, and the negative effects of oil spills have all prompted researchers to look for alternate sources of fuel for the production of energy (Yildirim et al, 2021). Additionally, the price of non-renewable fossil fuels has increased demand for affordable, renewable energy sources like solar, wind, and biofuels (Ahmed El-Imam et al, 2019a).…”

“…In Nigeria, agricultural operations result in the production of large amounts of lignocellulosic biomass, the majority of which pollute the environment by littering or feeding animals with low-quality feed (Ahmed El-Imam et al, 2019b;Hassan et al, 2019). In order to disrupt the complex structure of lignocellulosic biomass and separate the complex sugars into their monomeric molecules, a pretreatment stage is required (Ahmed El-Imam et al, 2013;Yildirim et al, 2021).…”