Bioreactors for lignocellulose conversion into fermentable sugars for production of high added value products.

Rossana Liguori,Olimpia Pepe,Valeria Ventorino,Vincenza Faraco

doi:10.1007/s00253-015-7125-9

Rossana Liguori, Olimpia Pepe + Show 2 more

Open Access

https://doi.org/10.1007/s00253-015-7125-9

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Abstract

Lignocellulosic biomasses derived from dedicated crops and agro-industrial residual materials are promising renewable resources for the production of fuels and other added value bioproducts. Due to the tolerance to a wide range of environments, the dedicated crops can be cultivated on marginal lands, avoiding conflict with food production and having beneficial effects on the environment. Besides, the agro-industrial residual materials represent an abundant, available, and cheap source of bioproducts that completely cut out the economical and environmental issues related to the cultivation of energy crops. Different processing steps like pretreatment, hydrolysis and microbial fermentation are needed to convert biomass into added value bioproducts. The reactor configuration, the operative conditions, and the operation mode of the conversion processes are crucial parameters for a high yield and productivity of the biomass bioconversion process. This review summarizes the last progresses in the bioreactor field, with main attention on the new configurations and the agitation systems, for conversion of dedicated energy crops (Arundo donax) and residual materials (corn stover, wheat straw, mesquite wood, agave bagasse, fruit and citrus peel wastes, sunflower seed hull, switchgrass, poplar sawdust, cogon grass, sugarcane bagasse, sunflower seed hull, and poplar wood) into sugars and ethanol. The main novelty of this review is its focus on reactor components and properties.

Highlights

IntroductionThe use of crops as renewable sources of energy and compounds in alternative to fossil resources can promote a sustainable development avoiding the problems of shortage of fossil feedstock (Liguori et al 2013; Kajaste 2014), but it generates problems in the agricultural market since their cultivation increases the lands subtracted to the food production and rising global food prices (Scheidel and Sorman 2012)
The use of crops as renewable sources of energy and compounds in alternative to fossil resources can promote a sustainable development avoiding the problems of shortage of fossil feedstock (Liguori et al 2013; Kajaste 2014), but it generates problems in the agricultural market since their cultivation increases the lands subtracted to the food production and rising global food prices (Scheidel and Sorman 2012).To limit the competition between the food- and the non food-crop lands, the cultivation of dedicated energy crops in marginal lands non appropriate for the traditional food crops is spreading throughout the world (Popp et al 2014)
This review summarizes the last advances in the bioreactor field, with main focus on the new configurations and the agitation systems, for conversion of dedicated energy crops and residual materials into sugars and ethanol by separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF) and consolidated bioprocessing (CBP) (Fig. 2)

Summary

Introduction

The use of crops as renewable sources of energy and compounds in alternative to fossil resources can promote a sustainable development avoiding the problems of shortage of fossil feedstock (Liguori et al 2013; Kajaste 2014), but it generates problems in the agricultural market since their cultivation increases the lands subtracted to the food production and rising global food prices (Scheidel and Sorman 2012). The saccharification was performed at 50 °C with 15 FPU of Spezyme CP cellulase enzyme (Genencor) per gram of cellulose, at speed of 250 rpm in flasks and 2 rpm in bioreactor The latter system allowed to reach a glucose yield of 60 %, a value 10 % higher than that obtained in flasks (50 %) and, within the first hours of the hydrolysis reaction, a quick decrease in torque was observed, allowing a low-energy consumption. The experiments were conducted in the 5-L bioreactor, performing a prehydrolysis step for 12 h at 50 °C followed by the SSF step at 37 °C to allow the S. cerevisiae DQ1 growth They demonstrated how the new agitation system improved the ethanol yield: 51.0 g L−1 of ethanol were obtained at the end of SSF by using the double helical impeller, respect to the 43.9 g L−1 reached in the reactor equipped with the Rushton impeller.

L fermentation reactor 2L

Findings

Conclusions