Page 286 - Refining Biomass Residues for Sustainable Energy and Bioproducts

254 Refining Biomass Residues for Sustainable Energy and Bioproducts

12.53 g/L in 1 L parallel fermenter with a productivity of 0.32 and 0.13 g/L/h,
respectively.
Pentose-rich acid-pretreated liquor from rice straw as a cosubstrate for 1,3-pro-
panediol production by Klebsiella pneumoniae PD41 was reported by Vivek et al.
(2018). The study revealed that an addition of acid pretreatment liquor (0.5% v/v)
as a cosubstrate resulted in the improved production of 1,3-propanediol (20.88 g/L)
with a productivity of 0.87 g/L/h.
Cao et al. (2015) reported 1,2,4-butanetriol production from renewable biomass.
In this study a recombinant strain capable of pentose utilization was used for the
production of 1,2,4-butanetriol. The study revealed that under optimized conditions
the engineered strain can efficiently convert xylose to 1,2,4-butanetriol. A maxi-
mum yield of 1,2,4-butanetriol is 3.92 g/L from 20 g/L of xylose with a conversion
efficiency of 27.7%.
Potential of oil palm front hydrolyzate for 2,3-butanediol production by
Enterobacter cloacae SG1 was evaluated by Hazeena et al. (2016). Nondetoxified
oil palm hydrolyzate was used as the sole carbon source which resulted in a produc-
tivity of 7.67 g/L. With glucose as a carbon source the strain produced 14.67 g/L of
2,3-butanediol. Fine tuning of various process parameters affecting 2,3-butanediol
production can improve the yield.

11.3 Lignin valorization

Lignin is the second abundant polymer and a highly branched macromolecule that
finds applications in biological, pharmaceutical, pulping, biosorption (Ge and Li,
2018), and polymer industries. Lignin can be used for the controlled release of her-
bicides and pesticides. It is used for the controlled release of urea that is highly
water soluble and leads to excess nitrogen level in the soil (Mulder et al., 2011).
Since urea got incorporated in the lignin layer, it resulted in a coating with low
water resistance. The study revealed that coating with lignin is an economically via-
ble strategy for a controlled release of urea. Lignosulfates are widely used as a
binding and dispersing agent (Stewart, 2008).

11.4 Conclusion and future perspectives

Agroresidues serve as a potential feedstock for the production of different value-added
products. Even though several R&D activities are going on throughout the world and
the technology for the conversion of lignocellulosic biomass to various products is
already proved, still an economically viable process is lacking. Hence fine tuning at
each unit operations as well as development of suitable consortium or genetically modi-
fied strains is required for an improved product yield and process efficiency.
Development of engineered strains or consortium that can grow on mixed agroresidues
and in the presence of inhibitors will reduce the overall process economics. Adopting a
biorefinery approach may lead this to a reality in the near future.