Profiling of Chemical and Structural Composition of Lignocellulosic Biomasses in Tetraploid Rice Straw

Abstract

The improvement of the saccharification of rice straw is one of the strategies to reduce the sophisticated pretreatment that results in high cost and is unfriendly to the environment. We explored the cell wall features in tetraploid rice and highlighted the enhanced saccharification of tetraploid with large biomass. Results showed that lignin content and S/G ratio reduced to 17.09% and 0.37, respectively, in tetraploid straw by the determination of the pyGC-MS method. After the pretreatment, the cellulose crystallinity index decreased from 63.22% to 57.65% in tetraploid straw, which is lower than that of pretreated diploid straw. Surface topological analysis of SEM images indicated that tetraploid straw was more susceptible to the pretreatment. Tetraploid straw showed a strong advantage in the process of enzymatic hydrolysis. The enzyme efficiency reached the highest value of 77.60%, and the rate of enzyme reaction was improved to make the reaction saturated earlier than conventional rice. We concluded that the high saccharification has resulted from the alteration of lignin and cellulose in tetraploid rice. Our research provides an improved green feedstock for bioenergy, and the tetraploid rice straw shows the potential utilization value in bioethanol production.

Insights into the Molecular Regulation of Lignin Content in Triploid Poplar Leaves

“…Compared with Arabidopsis diploids, the lignin contents of tetraploids, hexaploids, and octaploids were decreased by 20%, 50%, and 55%, respectively [14]. A similar phenomenon was found for polyploid crops such as rice and potatoes; the lignin content of polyploids was significantly lower than that of diploids [15,16].…”

“…From the results of our study, we suppose that polyploids have larger cells, usually accompanied by decreased cell-surface areas per unit volume, which possibly decrease the demand for lignin accumulation. Lignin content is usually reduced in multiple polyploid plants, such as poplar in this study, shrub willow, Arabidopsis, rice, and potato [12][13][14][15][16]. In contrast, the cellulose and hemicellulose contents of polyploids showed different trends in different species.…”

“…In contrast, the cellulose and hemicellulose contents of polyploids showed different trends in different species. For example, the cellulose content increased in triploid shrub willow [13], while it decreased in polyploid Arabidopsis, tetraploid rice, and tetraploid potato [14][15][16]. These results indicated that triploids may have a certain mechanism of regulating lignin biosynthesis to adapt their own demands, which are usually achieved by decreasing the expression of lignin structural genes and changing the expression of transcription factors, together regulating lignin biosynthesis.…”

Rice Straws With Different Cell Wall Components Differ on Abilities of Saccharification

“…Although lot of work has been done on crop improvement for high biomass yield, improving the pretreatment process and using biotechnological methods to increase the saccharification capacity could also improve straw utilization (Tian et al, 2018 ). Existing studies have shown that many crops have unique biomass composition, but knowledge about difference in biomass composition between high-cultivated varieties derived from same parents is either lacking or only superficial (Chen et al, 2020 ; Samavi and Rakshit, 2020 ). For example, rice varieties cultivated in different regions of the world might have different straw cell wall composition, so application of one pretreatment technology for straw conversion to bioethanol is undesirable (Gao et al, 2005 ).…”

“…So many factors of the cell wall structures might affect pretreatment effect (Li et al, 2010 ; Zhang et al, 2011 ). For example, crystalline cellulose is not easily decomposed, and lignin and hemicellulose affect the accessibility of enzymes (Lenting and Warmoeskerken, 2001 ; Van Wyk, 2001 ; Qian et al, 2005 ; Brandt et al, 2013 ; Chen et al, 2020 ). Various pretreatment methods are available, including chemical biological and physical methods.…”