(674b) Inhibitory Effects of Lignocellulosic Degradation Compounds From Hydrolysate On Microbial Oil Production

Inhibitory
effects of lignocellulosic degradation compounds from hydrolysate on microbial
oil production.

Jijiao Zeng, Xiaochen
Yu, Yubin Zheng, Shulin Chen*

Department of
Biological Systems Engineering, Washington State University, Pullman,
Washington 99164-6120, USA

*Corresponding author.
Tel: +1 509 335 3743; fax: +1 509 335 2722.

E-mail address: chens@wsu.edu

Abstract:

Recently microbe based lipid has attracted great
attentions due to its high potential for "drop in" fuel production.
Differentiation with phototrophic algal lipid, oleaginous yeast/fungi shows notably
capability to accumulate lipid on utilization of lignocellulosic biomass which are
recognized as most promising renewable resource for bio-fuel production.
However, traditional pretreatment technologies, such as dilute acid, producing
hydrolysate contain various carbonhydrate and lignin derivative compounds. These
weak acids, furan aldehydes and phenolic aldehydes extensively inhibit
microbial fermentation. Therefore, understanding their inhibitory effects to
oleaginous yeast/fungi gives critical information to guide hydrolysis process
for microbial oil production. In this study, the lipid accumulation by Cryptococcus curvatus and Mortierella isabellina was prudently
investigated in the presence of eight representative inhibitors.  The results showed that these two
strains have unexpectable tolerance to inhibitors in wide range of concentrations
which overridden most reported value in lignocellulosic hydrolysate. Among the
inhibitors, furfural and three phenolic aldehydes strongly repressed the growth
of both yeast and fungus when the concentrations rose to 2 g/L (Fig.1A). The best
performances on specific inhibitors were also observed with slight difference
between yeast and fungi that might be resulted from their enzyme system and
cultural conditions. Furthermore, the inhibitory effects indicated dependence
on inoculum size and had minor influences on lipid content and fatty acid
composition (Fig 1B). In short, our work demonstrated that Cryptococcus curvatus and Mortierella
isabellina can tolerate high concentration of inhibitors which imply their
possibility on economically competitive lipid production using non-detoxified
hydrolysate.

Figure 1. Effects of inhibitors on biomass (A) and
lipid (B) production by Cryptococcus
curvatus