Elsevier

Bioresource Technology

Volume 116, July 2012, Pages 540-544
Bioresource Technology

Short Communication
Gamagrass varieties as potential feedstock for fermentable sugar production

https://doi.org/10.1016/j.biortech.2012.04.050Get rights and content

Abstract

To evaluate the potential of gamagrass as a feedstock for biofuels, seven gamagrass varieties were analyzed for their chemical composition and subjected to pretreatment at 121 °C using 1% NaOH/H2SO4 (w/w) for 60 min and enzymatic hydrolysis for fermentable sugar production. Based on total sugar yield, the varieties Eagle Point Devil Corn and Sun Devil were selected for NaOH and H2SO4 pretreatment, respectively. The investigation on pretreatment conditions showed that, the conditions applied in gamagrass variety screening (121 °C, 1% NaOH/H2SO4, 60 min) were sufficient to maximize sugar production, such that the total sugar yield of Eagle Point Devil Corn reached 479.6 mg g−1 after NaOH pretreatment and that of Sun Devil reached 456.5 mg g−1 raw biomass after H2SO4 pretreatment. Compared with other potential energy crops including switchgrass and Bermuda grass, gamagrass gave a higher sugar yield after NaOH pretreatment and a comparable sugar yield after H2SO4 pretreatment.

Highlights

► Gamagrass had a higher carbohydrate content than switchgrass and Bermuda grass. ► Biochemical conversion of gamagrass resulted in high sugar yields. ► Gamagrass is a promising feedstock for biofuels.

Introduction

Although encouraging progress has been made over the past decade towards cost-effective ethanol production from grasses such as switchgrass (Panicum virgatum) and Bermuda grass (Cynodon dactylon), commercialization of ethanol production based on these herbaceous feedstocks has not been realized due to biomass recalcitrance. Since significant variations in biomass structure and composition exist among different grasses, which might substantially affect the susceptibility of grass to biochemical conversion and its sugar production ability, it is necessary to explore other under-or un-explored grasses and evaluate their potential as feedstocks for biofuels. Gamagrass (Tripsacum dactyloides) is a perennial warm-season C4 grass native to the US and has the potential to produce large amounts of biomass in the southeastern part of the country. Gamagrass yields of up to 19.0 t ha−1 y−1 have been reported so far (USDA-NRCS, 2007), which are comparable with those of switchgrass and Bermuda grass (Xu et al., 2011, Keshwani and Cheng, 2009). Additionally, it has many other desirable characteristics as an energy crop, which include high carbohydrate content, adaptation to different soil and climate conditions, non-invasiveness, and easy integration into existing farming operations (Ge et al., 2012, Lemus and Parrish, 2009).

In this study, to evaluate the biofuel potential of gamagrass, seven gamagrass varieties were screened for fermentable sugar production via biochemical conversion. Sodium hydroxide (NaOH) and sulfuric acid (H2SO4) pretreatments were applied to improve digestibility of gamagrass and followed by enzymatic hydrolysis for sugar production. The gamagrass variety with greatest potential was determined based on the release of total sugars during biomass conversion. Because of the crucial role that pretreatment plays in reducing biomass recalcitrance, effects of pretreatment conditions on sugar production were further investigated to identify optimal process conditions. A comparison of the potential of gamagrass relative to switchgrass and Bermuda grass was also provided.

Section snippets

Methods

The study consisted of two steps: gamagrass variety screening and pretreatment optimization. During varietal screening, gamagrass was pretreated at 121 °C using 1% NaOH or H2SO4 (w/w) for 60 min to improve its enzymatic digestibility and the pretreated biomass was subjected to enzymatic hydrolysis at excess enzyme loadings for sugar production. The pretreatment conditions applied were determined according to our previous work with other herbaceous biomass (Xu et al., 2010a, Wang et al., 2010,

Characteristics of gamagrass varieties

Different varieties of gamagrass studied were found to have a total carbohydrate content of 57.2–64.8%, which was higher than that of Performer switchgrass (53.5%) and coastal Bermuda grass (44.9%) (Table 1). The variety Eagle Point Devil Corn had a total carbohydrate content significantly (P < 0.05) higher than most other varieties except Door and the highest glucan content among all varieties. The lignin content of gamagrass (22.9–25.6%) was higher than that of Performer switchgrass (21.4%) and

Conclusions

Gamagrass varieties have higher carbohydrate contents than Performer switchgrass and coastal Bermuda grass. After NaOH pretreatment at the best conditions (121 °C, 1% NaOH, 60 min), the total sugar yield of Eagle Point Devil Corn reached 479.6 mg g−1 raw biomass, 66.1% of the theoretical yield. After H2SO4 pretreatment at the best conditions (121 °C, 1% H2SO4, 60 min), the total sugar yield of Sun Devil reached 456.5 mg g−1 raw biomass, 66.8% of the theoretical yield. The sugar yield of gamagrass was

Acknowledgements

The authors would like to thank Mr. Sam Brake and Mr. Phil Sheridan at the Biofuels Center of North Carolina for assistance in obtaining the feedstock samples. We would also like to thank Dr. Dhanalekshmi Savithri for her assistance in chemical analyses.

References (17)

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