Simultaneous Saccharification and Fermentation of Pine Sawdust (Pinus pseudostrobus L.) Pretreated with Nitric Acid and Sodium Hydroxide for Bioethanol Production

Juan Carlos Farías-Sánchez, Ulises Velázquez-Valadez, María Guadalupe Pineda-Pimentel, Javier López-Miranda, Agustín Jaime Castro-Montoya, Artemio Carrillo-Parra, Alfonso Vargas-Santillán, José Guadalupe Rutiaga-Quiñones

Abstract


With the purpose of taking advantage of pine sawdust residue coming from a sawmill located in Michoacán, México, a pretreatment with nitric acid and sodium hydroxide was performed. Also, the production of bioethanol by enzymatic hydrolysis was investigated. Using a response surface method, the intermediate points for the optimal HNO3 concentration were determined. Results showed that using HNO3 as a pretreatment leads to higher ethanol yields at an optimal concentration of 10.90% HNO3. After a 30-min pretreatment with 10.90% HNO3 at 114.32 °C, followed by 1% NaOH and enzymatic hydrolysis performed in shaker at a pH of 4.8 and 150 rpm for 72 h, with an enzyme loading of 25 FPU/g of total carbohydrates, the reducing sugars concentration was 99.2% (conversion of polysaccharides to monomers). On the other hand, the ethanol yield obtained from the simultaneous saccharification and fermentation treatment was 15.0 g/L, and the separate hydrolysis and fermentation was 17.1 g/L at a pH of 4.8 and 150 rpm with 1X107 Cel/mL of Saccharomyces cerevisiae and an enzymatic loading of 25 FPU/g of total carbohydrates. When comparing the results obtained with literature data, it is concluded that this procedure is suitable to exploit the lignocellulosic wastes from the Indigenous Community of San Juan Nuevo Parangaricutiro, Michoacán, Mexico.

Keywords


Reducing sugars; Enzymatic hydrolysis; Pine sawdust; Pinus pseudostrobus

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