Integrated production of second generation ethanol and lactic acid from steam-exploded elephant grass

Authors: MONTIPÓ, SHEILA - Universidade De Caxias Do Sul; BALLESTEROS, IGNACIO - Research Centre For Energy, Environment And Technology; FONTANA, ROSELEI - Universidade De Caxias Do Sul; Liu, Siqing; MARTINS, AYRTON - Universidade Federal De Santa Maria; BALLESTEROS, MERCEDES - Research Centre For Energy, Environment And Technology; CAMASSOLA, MARLI - Universidade De Caxias Do Sul

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2017
Publication Date: 11/3/2017
Citation: Montipó, S., Ballesteros, I., Fontana, R.C., Liu, S., Martins, A.F., Ballesteros, M., Camassola, M. 2017. Integrated production of second generation ethanol and lactic acid from steam-exploded elephant grass. Bioresource Technology. 249:1017-1024. doi: 10.1016/j.biortech.2017.11.001.
DOI: https://doi.org/10.1016/j.biortech.2017.11.001

Interpretive Summary: This paper reports the fermentative production of ethanol and lactic acid from pretreated lignocellulosic materials of Pennisetum purpureum, known as elephant grass (EG). EG is a type of forage with high photosynthetic efficiency and biomass productivity. EG is used here for parallel production of ethanol and lactic acid. After steam explosion of EG, the solids were treated with cellulases and then used for simultaneous sacchari'cation and fermentation by S. cerevisiae CAT-1, producing 42.25g L-1 ethanol. The liquor portion of the pretreated EG containing xylooligosaccharides was used for lactic acid production by using L. buchneri NRRL B-30929, resulting in 13.35g L-1 of lactic acid. This is the first report using EG in a biorefinery platform and the process designed in this study will be valuable for cost effective fuel and chemical productions.

Technical Abstract: Elephant grass was subjected to steam explosion to enhance cellulose accessibility and convert it into ethanol. After catalyzed pretreatment at 190°C for 5 min, enzymatic hydrolysis was carried out using high rate of solids loading combined with different enzyme dosages. Assays employing 20% (w/v) solids loading and an enzyme dosage of 20 FPU g-1 substrate led to a yield of 86.02g glucose released per 100g potential glucose in the water insoluble solids. This condition was selected to carry out the simultaneous sacchari'cation and fermentation procedure through S. cerevisiae CAT-1, producing 42.25g L-1 ethanol with a yield of 74.57% regard to the maximum theoretical. The liquor containing xylooligosaccharides was successfully converted into lactic acid using L. buchneri NRRL B-30929, resulting in 13.35g L-1 with a yield of 68.21% in relation to the maximum theoretical.