Microwave‐based alkali pretreatment of switchgrass and coastal bermudagrass for bioethanol production

Abstract

Switchgrass and coastal bermudagrass are promising lignocellulosic feedstocks for bioethanol production. However, pretreatment of lignocelluloses is required to improve production of fermentable sugars from enzymatic hydrolysis. Microwave‐based alkali pretreatment of switchgrass and coastal bermudagrass was investigated in this study. Pretreatments were carried out by immersing the biomass in dilute alkali reagents and exposing the slurry to microwave radiation at 250 W for residence times ranging from 5 to 20 min. Simons' stain method was used to quantify changes in biomass porosity as a result of the pretreatment. Pretreatments were evaluated based on yields of total reducing sugars, glucose, and xylose. An evaluation of different alkalis identified sodium hydroxide as the most effective alkali reagent for microwave‐based pretreatment of switchgrass and coastal bermudagrass. 82% glucose and 63% xylose yields were achieved for switchgrass and 87% glucose and 59% xylose yields were achieved for coastal bermudagrass following enzymatic hydrolysis of biomass pretreated under optimal conditions. Dielectric properties for dilute sodium hydroxide solutions were measured and compared with solid losses, lignin reduction, and reducing sugar levels in hydrolyzates. Results indicate that dielectric loss tangent of alkali solutions is a potential indicator of the severity of microwave‐based pretreatments. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010

Sodium Hydroxide Pretreatment and Enzymatic Hydrolysis of Oil Palm Mesocarp Fiber

“…It can be observed that more severe pretreatment with higher NaOH concentration cause greater disruption on the fiber structure and creating number of large pores. This phenomenon significantly increases the accessibility of enzyme during hydrolysis process [3]. After the enzymatic hydrolysis, the structure mesocarp fiber was completely destroyed and wall of the fibers was completely ruptured as shown in Fig.…”

“…Due to the enormity of the plantation industry, about 10.9 million tons of oil palm mesocarp fiber is being produced annually as agriculture waste and contributes to the accumulation of lignocellulosic waste and cause emission of greenhouse gas to the environment [1]. Traditionally oil palm mesocarp fiber is either used in mulching or incinerated, however both Manuscript received February 9, 2013; revised April 12, 2013 Generally, lignocellulosic biomass consists of three main groups of polymer that are cellulose, hemicelluloses and lignin [3]. These compounds are also major components in oil palm biomass [4].…”

Triacylglycerol Production from Corn Stover Using a Xylose-Fermenting Rhodococcus opacus Strain for Lignocellulosic Biofuels

“…Switchgrass is recognized as a desirable energy crop due to high productivity, low agricultural inputs for harvest, and protection of the environment [29]. Corn stover, consisting of stalks, cobs and leaves that remain in fields after the gain harvest, has a carbohydrate content of approximately 60% of the dry weight [30].…”

Microwave-assisted pretreatment technologies for the conversion of lignocellulosic biomass to sugars and ethanol: a review

“…In a similar study, microwave-based alkali pretreatment of switchgrass and coastal bermudagrass resulted in better sugar yields during subsequent enzymatic hydrolysis; as high as 82% glucose and 63% xylose yields for switchgrass and 87% glucose and 59% xylose yields for Bermuda grass were reported [38].…”

“…Microwave irradiation of biomass is a promising pretreatment process because it utilizes thermal and specific (non-thermal) effects generated by microwaves in aqueous environments [38]. Low temperature pretreatment is generally preferred to avoid hemicellulose degradation and to improve the pentose yield [39].…”