Page 102 - Lignocellulosic Biomass to Liquid Biofuels

78 Lignocellulosic Biomass to Liquid Biofuels

• White rot Basidiomycetes (Trametes versicolor, Flammulina velutipes, Phlebia
sp., Peniophora cinerea, Trametes suaveolens)
• Yeasts (K. marxianus, Clavispora, cryophilic Mrakia blollopis)
In addition, two genetic engineering strategies have been extensively
described [85]:
1. Engineering cellulase producers (C. thermocellum, Clostridium cellulolyticum,
T. saccharolyticum, Thermoanaerobacterium aotearoense, Thermoanaerobacter
mathranii, Caldicellulosiruptor bescii, Geobacillus thermoglucosidasius, K. oxyto-
ca, T. reesei [59],and F. oxysporum) to be ethanologenic
2. Engineering ethanologens (S. cerevisiae, K. marxianus, Hansenula poly-
morpha, Z. mobilis, E. coli, P. stipitis, F. velutipes) to be cellulolytic
Hasunuma et al. [72] investigated the ethanol production from cellu-
losic and hemicellulosic materials with thermotolerant yeast strains in SSF
or CBP at elevated temperature. In particular, they focused on the follow-
ing yeast strains: K. marxianus, H. polymorpha, Candida glabrata, S. cerevisiae,
Pichia kudriavzevii, and Debaromyces hansenii. Svetlitchnyi et al. [86] isolated
other thermophilic bacteria suitable for a single-step conversion of ligno-
cellulosic biomass to ethanol at temperatures .70°C.

3.2.2 Biobutanol
Biobutanol is produced from the same raw material as bioethanol, and it
can be used as biofuel or fuel additive with several advantages over etha-
nol, because it has similar characteristics with gasoline.
A sustainable industrial-scale biobutanol production is possible by
different strategies, including choice of feedstock, product toxicity to
strains, multiple end products, and downstream processing of alcohol
mixture [87].

Butanol can be generated as a product of anaerobic ABE (acetone
butanol ethanol) fermentation of lignocellulosic biomasses or other feed-
stocks by a number of solventogenic Clostridium species [88], following
delignification and hydrolysis pretreatments. Clostridium bacteria can
metabolize different sugars, amino and organic acids, polyalcohols and
other organic compounds to butanol, and other solvents [89]. The most
intensively studied solvent-producing species is C. acetobutylicum [90,91]
that gives a mixture of fermentation products composed of ABE at a ratio
of 3:6:1. Other strains involved in ABE fermentation are Clostridium
beijerinckii [92 100], Clostridium pasteurianum [92,101], Clostridium saccharo-
butylicum [94,102 106], and Clostridium saccharoperbutylacetonicum