Liquid nitrogen pretreatment of eucalyptus sawdust and rice hull for enhanced enzymatic saccharification

- Cryogenic grinding with liquid nitrogen is a method of powdering plant biomass.
- Cryocrushing was used for the first time as pretreatment of lignocelluloses.
- Cryocrushing disorganized the fibers, without lignin destruction.
- Saccharification of eucalyptus sawdust and rice hull improved more than 10 times.
- Cryocrushing did not improve the saccharification of pure cellulose.

In this work, liquid nitrogen was used for the first time in the pretreatment of plant biomasses for purposes of enzymatic saccharification. After treatment (cryocrushing), the initial rates of the enzymatic hydrolysis of eucalyptus sawdust and rice hull were increased more than ten-fold. Cryocrushing did not modify significantly the contents of cellulose, hemicellulose and lignin in both eucalyptus sawdust and rice hulls. However, substantial disorganization of the lignocellulosic materials in consequence of the pretreatment could be observed by electron microscopy. Cryocrushing was highly efficient in improving the saccharification of the holocellulose component of the plant biomasses (from 4.3% to 54.1% for eucalyptus sawdust and from 3.9% to 40.6% for rice hull). It is important to emphasize that it consists in a simple operation with low requirements of water and chemicals, no corrosion, no release of products such as soluble phenolics, furfural and hydroxymethylfurfural and no waste generation.

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