Background: Rapid depletion in petroleum resources coupled with environmental pollution
from the burning of coal and oil has led to the search for alternative energy sources. Lignocellulostarch
biomasses (LCSBs) comprising peels of root crops and vegetables causes environmental
hazards due to their non-judicious disposal. They are highly recalcitrant to breakdown necessitating
effective pretreatment to exploit their use as bioethanol feedstock. Although microwave (MW)-
assisted chemical pretreatment has emerged as a cost-effective process for lignocellulosic biomass,
there is no information on its efficacy in deconstructing LCSBs that also contain appreciable quantities
Methods: Response surface methodology was adopted to study the impact of three parameters such as
MW irradiation power, dilute sulphuric acid (DSA) concentration and irradiation time on the
polysaccharide (cellulose, hemicellulose and starch) and lignin changes as well as the reducing sugar
(RS) recovery after pretreatment. The optimized system was saccharified using triple enzyme cocktail
to assess the RS recovery and saccharification kinetics.
Results: Microwave power had the greatest influence in deconstructing the LCSBs and maximum
quantities of hemicellulose (88%), followed by cellulose (65%), starch (42%) and lignin (32-42%)
were removed under RSM optimized conditions (600 W; 0.1M DSA; 7 min irradiation time).
Pretreatment Efficiency ranged from 52-62% indicating high RS release from the LCSBs. The
residues after optimized pretreatment when saccharified using triple enzyme cocktail containing
cellulase, xylanase and Stargen (starch hydrolyzing enzyme complex) for 120 h resulted in very high
RS recovery (57-71 g L-1).
Conclusion: The Overall Conversion Efficiency of carbohydrates to RS was very high (85-96%),
indicating that the MW-assisted DSA pretreatment followed by triple enzyme-based saccharification
system is an effective strategy for enhancing fermentable sugar yield from lignocellulo-starch