73. Kumar, Sandeep; Gupta, Rajesh; Lee, Y. Y.; Gupta, Ram B.. Cellulose pretreatment in subcritical water: Effect of temperature on molecular structure and enzymatic reactivity. Bioresource Technology (2010), 101(4), 1337-1347.
Abstract
Microcryst. cellulose (MCC)
was pretreated with subcrit. water in a continuous flow reactor for
enhancing its enzymic reactivity with cellulase enzyme.
Cellulose/water suspension was mixed with subcrit. (i.e., pressurized
and heated) water and then fed into the reactor maintained at a const.
temp. and pressure. After the reaction, product was immediately
cooled in a double-pipe heat exchanger. The solid portion of the
product (i.e., treated MCC) was sepd. and tested for mol. structure and
enzymic reactivity. Expts. were conducted at temps. ranging from
200 to 315 C, at 27.6 MPa, and for 3.4-6.2 s reaction times. The
treated MCC was characterized for d.p. (DPv) by viscosimetry, and
crystallinity by X-ray diffraction (XRD). In addn., differential
scanning calorimetry and SEM (SEM) analyses were carried out to study
any transformation in the cellulose structure. As expected, DPv
of cellulose steadily decreased with increase in the pretreatment
temp., with a rapid drop occurring above 300 C. On the other
hand, XRD anal. did not show any decrease in crystallinity upon
pretreatment but, partial transformation of celluloses I-II structure
was noticed in the MCC treated at 300 C. Development of surface
cracks and trenches were obsd. in the SEM images for all the treated
samples. Enzymic reactivity was increased after the treatment at
300 C.
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