Pentose rich acid pretreated liquor as co-substrate for 1,3-propanediol production

Lignocellulosic biomass is considered to be a potential raw material for production of renewable fuels like bioethanol and biodiesel. Cellulose and hemicelluloses constitute major portion of the lignocellulosic biomass. Cellulose can be converted to glucose by hydrolysis and subsequently to ethanol by fermentation. The hemicellulosic portion mostly contains pentose sugars which cannot be utilized by many microorganisms for ethanol production. Acid pretreatment results in separation of a pentose-rich fraction which can be utilized for the production of various high value chemicals. The present study evaluates the utilization of pentose sugars as co-substrate, along with biodiesel industry-generated crude glycerol, for the production of 1,3-propanediol (1,3-PDO). Bioconversion of these low value byproducts into a high value chemical would be an economically advantageous strategy in terms of waste disposal for biorefineries. In this study, the production of 1,3-propanediol from the acid pretreated liquor obtained from rice straw was evaluated using Klebsiella pneumonia. Different carbon sources like pure hexose and pentose sugars, mixed pentose sugar containing acid pretreated liquor (APL) from rice straw and different concentrations of pentose sugars and acid pretreated liquor were evaluated. There is 65% increase in titers from 9.55 g/L to 15.75 g/L using APL as co-substrate. With addition of 0.5% (v/v) APL, 1,3-propanediol production reached 20.88 g/L with 0.69 g/g yield and 0.87 g/L/h productivity. The study comprehensively explains the behavior of Klebsiella pneumoniae strain utilizing pentose rich APL and crude glycerol which enroute to an integrated biorefinery approach.