Abstract
Lignocellulosic
bioethanol production now-a-days is gaining increasing interest due to global
warming, hike in oil price etc. But there are several technological and other
challenges associated with bioethanol production. Technological challenges are
development of efficient pretreatment step which can significantly degrade
lignin without altering carbohydrates, efficient hydrolysis step and
development of fermentation step which can utilize both pentose and hexose
sugars. The present study has focused on bioprocess development for bioethanol
production from a mixture of food wastes (spinach, cabbage, peels of onion and
orange). First liquid hot water (LHW) pretreatment of food waste was optimized
by varying different parameters (temperature, incubation time and substrate
concentration). Maximum reducing sugar yield (525.60 mg/gram dry substrate) was
found at substrate concentration 10% (w/v), temperature 160 oC and incubation
time 30 min. After optimization, LHW pretreated biomass was characterized using
Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD),
Scanning electron microscopy (SEM) and biochemical composition analysis.
Further, pretreated biomass was hydrolysed using whole cells of Fusarium
incarnatum KU377454 (locally isolated strain) without addition of any enzymes.
It showed maximum reducing sugar yield of 580.95 mg/gram dry substrate) within
3 days of incubation at 30 oC. The produced sugar hydrolysate was further
fermented using co-cultures of hexose fermenting strain (Sacchromyces
cerevisiae) and pentose fermenting strain (F. oxysporum). Maximum ethanol
production (3.25%, v/v) was observed after 48 h of incubation at 35 oC. The
present study, reports development of efficient thermal pretreatment without
addition of any chemicals. Further carbohydrates, part of pretreated biomass
were converted into reducing sugars by whole fungal strain without the use of
any costly chemicals. Lastly, fermentation process was optimized using
co-culture strategy which yielded maximum ethanol from both pentose and hexose
sugars. This study can be useful for commercial bioethanol production from food
waste.