Lignocellulose detoxification

Speakers were asked to provide quantitative data on the performance of different xylose- (or, in one instance, arabinose-) fermenting strains in laboratory media and, where possible, in "industrial" media prepared by hydrolysis of native lignocellulosic substrates. The data provided are presented in Table 1, which gives an indication of the performance of the various strains but should not be taken as a rigorous comparison. In particular, there is considerable variation in the extent of nutritional supplementation of the various media and the degree of detoxification of the hydrolysates. References provided by some of the speakers are also given (1-6). 

Synthetic medium containing xylose or arabinose and one or more complex ingredients (unless otherwise indicated). b Mixed sugar hydrolysate of native lignocellulosic substrate lacking complex medium ingredients. Detoxification applied unless otherwise indicated. 

It is highly probable that in the reticulo-rumen many of the mineral deficiencies and/or toxicities noted in vitro would not occur because of the recycling of minerals and the detoxification ability of the microflora. However, from evidence available, some minerals can have a pronounced effect on lignocellulose breakdown and are in some instances the first limiting factor in rate and/or extent of lignocellulose degradation. 

Phenolic compounds from lignin degradation, furan derivatives (furfural and HMF) from sugar degradation and aliphalic acids (acetic acid, formic acid and levulinic acid) are considered to be fermentation inhibitors generated from pretreated lignocellulosic biomass (53). The formation of these inhibitors depends on the process conditions and the lignocellulosic feedstocks 54). Various methods for detoxification of the hydrolyzates have been developed (55). These include... 

Microorganisms metabolically engineered with improved inhibitor tolerance could reduce the need for detoxification process. Larsson et al. (766) developed a S. cerevisiae strain with enhanced resistance to phenolic fermentation inhibitors in lignocellulose hydrolyzates by heterologous expression of laccase. 

Palmqvist E, Hahn-Hagerdal B. (2000). Fermentation of lignocellulosic hydrolysates. 1 inhibition and detoxification. Bioresour Technol, 74, 17-24. 

Bioconversion of lignocellulose inhibitors and detoxification. Biotechnol. Biofuels, 6, 16. 

Mussatto, S.I. and Roberto, I.C. (2004) Alternatives for detoxification of diluted-acid lignocellulosic hydrolyzates for use in fermentative processes a review. Bioresour. Technol, 93 (1), 1-10. 

Jonsson, L.J., Alriksson, B., and Nilvebrant, N.-O. (2013) Bioconversion of lignocellulose inhibitors and detoxification. Biotechnol Biofuels,... 

Liu, Z.L. (2011) Molecular mechanisms of yeast tolerance and in situ detoxification of lignocellulose hydrolysates. Appl. Microbiol Biotechnol, 90, 809-825. 

Nilvebrant N, Reimann A, Larsson S, Jonsson L (2001) Detoxification of lignocellulose hydrolysates with ion-exchange resins. Appl Biochem Biotechnol 91-93 35-49 Olsson L, Hahn-Hagerdal B (1996) Fermentation of lignocellulosic hydrolysates for ethanol production. Enzym Microb Technol 18 312-331... 

Pais J, Farinha I, Serafim LS, Prieto MA, Arevalo-Rodriguez M, Reis MAM (2009) Bioplastics production from cheese whey by recombinantE. coli. New Biotechnol 25(Supp 1) S220-S220 Palmqvist E, Hahn-Hagerdal B (2000) Fermentation of lignocellulosic hydrolysates. I inhibition and detoxification. Bioresour Technol 74 17-24... 

The latter approach to remove fermentation inhibitors in lignocellulosic hydrolysate using whole cells was also the focus of study of Wierckx et al. (2010). In this study, the bacterium Cupriavidus basilensis HMF14 was identified as a promising detoxification bacterium, as it consumes HMF, furfural, acetic acid, and a wide... 

Palmqvist, E., Hahn-Hagerdal, B. Fennentation of lignocellulosic hydrolysates. I inhibition and detoxification. Bioresour Technol. 2000, 74,17-24. 

Detoxification procedures are often required for acidic and steam-exploded lignocellulosic hydrolysates, as variable concentrations of toxic furans (furfural and 5-HMF), lignin degradation compounds (aromatics and phenolics including vanillin, catechol, guaiacol, ferulic acid, syringaldehyde, and 4-hydroxy-... 

Larsson, S., A. Reimarm, N. Nilvebrant, L. Jonsson. 1999. Comparison of different methods for the detoxification of lignocellulose hydrolyzates of spruce. Appl. Biochem. Biotechnol. 77/79 91-103. 

---