With the depletion of petroleum resources and increasing demand on energy, lignocellulose derived ethanol seems to be the future of transportation fuels. Also, it is noticeable that the integrated biorefineries, which generate chemicals, materials, fuels and energy from the biomass, would replace the current petroleum refineries, moving the world toward a carbohydrate-based economy (Gnansounou 2009).

By-products like HSSL cannot be discharged into natural basins due to environmental concerns (211 g COD. L-1) and must be processed (Evtuguin et al. 2010). The biochemical processing of HSSL is a well-known approach to produce value-added products such as SCP and ethanol, among others (Busch et al. 2006).

As seen previously, biological detoxification of HSSL by P. variotti was possible and the fungal biomass obtained (2.0 g biomass/g substrate consumed) can be sold as SCP, for animal nutrition. For process optimization a Sequential Batch Reactor (SBR) was chosen and the same inoculum was used during three batches to treat fresh HSSL. Each cycle was ended when the acetic acid reached a non-inhibitory concentration for P. stipitis and this operating strategy provided high volumes of detoxified HSSL, for subsequent bioethanol fermentation (Pereira et al. 2011). With this detoxification process as well as with the described ion — exchange process (Xavier et al. 2010) HSSL can be further bioprocessed by P. stipitis, as reviewed before. The maximum concentration of ethanol attained was 8.1 g. L-1 with a yield of 0.49 g ethanol. g sugars-1 (Xavier et al. 2010). The bioethanol produced from HSSL, regarding the aforementioned fermentation results, may be estimated as high as 100 litters per one ton of pulp (Evtuguin et al. 2010).

Biopolymers are also important value-added products that can be produced within a biorefinery concept, being capable to replace fossil-fuels based polymers. Microbial mixed cultures (MMC) under aerobic dynamic feeding conditions (ADF) in HSSL, can utilize acetic acid for polyhydroxyalkanoates (PHAs) production. PHAs are biodegradable plastics that can be stored intracellularly by bacteria from renewable resources. A MMC culture was selected in a SBR under

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