Page 110 - Lignocellulosic Biomass to Liquid Biofuels

86 Lignocellulosic Biomass to Liquid Biofuels

thereby minimizing the total hydrolysis cost. Permeate acquired from UF
was concentrated by NF using NF270 membrane to concentrate glucose
3.5 times more from UF permeate, thus improving fermentation effi-
ciency as well as lower the cost of downstream processing of fermentative
2
product. Permeate flux for UF was 25.6 L/(m h) at 1.27 bar transmem-
2
brane pressure, whereas for NF flux reduced to 13.3 L/(m h) at 35 bar
pressure [198].
In another study, dilute alkali-treated wheat straw showed better recy-
cling of substantial amount of enzyme in contrast to adsorption recycling,
UF using glass microfiber membrane can efficiently retain BGL, thus
keeping away from the loading of BGL in successive round of hydrolysis,
thereby boosting the economics of enzymatic hydrolysis [193].
Recover and recycle of cellulase and cellobiase used in hydrolysis of
ammonia fiber explosion-treated corn stover can be efficiently attained by
UF using PES 76 mm, 10 kDa, membrane. Electro-UF, an advancement
of UF caused by intensification of UF by electric field, can efficiently lessen
concentration polarization as well as increase membrane flux using cation-
exchange membrane and polymeric membrane. Suitable conditions, that is,
low buffer concentration, room temperature, and high current, increase
the flux and sufficiently recover and recycle cellulase from hydrolizate of
acid-treated wheat straw. Concentration polarization resistance decreased
9 9
from 7.5 to 8 3 10 to 3 3.5 3 10 Pa s/m while increasing electric field
strength from 0 to 144 V/m. Thus flux is proportional to electric
field. Polymeric UF membrane can hydrolyze maximum amount of
microcrystalline cellulose pretreated with ionic liquid.
This process permits maximum recovery and recycling of cellulose
retaining its utmost activity for nine running cycle in semicontinuous pro-
cess. Continuous process with tangential flow ceramic UF membrane
shows constant permeate flux and glucose concentration at different
residence time proving itself as a good practice for cellulose hydrolysis
procedure [199].
Submerged vibration and stirring at membrane surface reduce fouling
and concentration polarization thus enhancing permeate flux [200]. All
the experimental studies reveal the importance of membranes and
membrane-assisted separation process for retrieving and reuse of cellulase
in an energy-efficient manner as well as reducing the cost of enzyme and
enzymatic hydrolysis step in recent fuel-grade bioethanol industry.
Tables 3.2 and 3.3 show the summary of membrane process assisted cellu-
lase recovery, respectively, for UF and other membrane-based processes