Lime pretreatment

Most mill solids are slightly toxic, predominantly from chlorination compounds in the wash waters from bleaching. This toxicity can be reduced with lime pretreatment and biological treatment. Toxicity has been the main concern of governmental regulating bodies in recent years. 

Enzyme activity loss because of non-productive adsorption on lignin surface was identified as one of the important factors to decrease enzyme effectiveness, and the effect of surfactants and non-catalytic protein on the enzymatic hydrolysis has been extensively studied to increase the enzymatic hydrolysis of cellulose into fermentable sugars [7, 9 19]. The reported study showed that the non-ionic surfactant poly(oxyethylene)2o-sorbitan-monooleate (Tween 80) enhanced the enzymatic hydrolysis rate and extent of newspaper cellulose by 33 and 14%, respectively [20]. It was also found that 30% more FPU cellulase activity remained in solution, and about three times more recoverable FPU activity could be recycled with the presence of Tween 80. Tween 80 enhanced enzymatic hydrolysis yields for steam-exploded poplar wood by 20% in the simultaneous saccharification and fermentation (SSF) process [21]. Helle et al. [22] reported that hydrolysis yield increased by as much as a factor of 7, whereas enzyme adsorption on cellulose decreased because of the addition of Tween 80. With the presence of poly(oxyethylene)2o-sorbitan-monolaurate (Tween 20) and Tween 80, the conversions of cellulose and xylan in lime-pretreated com stover were increased by 42 and 40%, respectively [23]. Wu and Ju [24] showed that the addition of Tween 20 or Tween 80 to waste newsprint could increase cellulose conversion by about 50% with the saving of cellulase loading of 80%. With the addition of non-ionic, anionic, and cationic surfactants to the hydrolysis of cellulose (Avicel, tissue paper, and reclaimed paper), Ooshima et al. [25] subsequently found that Tween 20 was the most effective for the enhancement of cellulose conversion, and anionic surfactants did not have any effect on cellulose hydrolysis. With the addition of Tween 20 in the SSF process for... 

Table 4 shows the effects of pretreatment time, temperature, and lime loading on TRS yield after hydrolysis for lime pretreatment of nonscreened bagasse. The statistical analysis was performed using the software Statistica (StatSoft, v. 7.0) and the confidence level considered was 90%. Significant effects are marked in italics. A statistical model is not presented because a linear model is not able to represent experimental behavior in this case. 

As screening is an expensive unit operation, we investigated not only the best result (lime pretreatment of screened bagasse) but also the two options for pretreatment with nonscreened bagasse alkaline peroxide and lime pretreatments. 

The effectiveness of alkaline hydrogen peroxide and lime pretreatment in improving sugar cane bagasse susceptibility to enzymatic hydrolysis was evaluated. Two complete 2x2x2... 

For nonscreened bagasse, the best results are for alkaline peroxide pretreatment performed with 5% FI2O2 at ambient temperature for 24 h. Lime pretreatment with 0.40 g lime/g dry biomass at 70 °C for 36 h also leads to high glucose yield. The choice between alkaline peroxide and lime pretreatment in this case is not straightforward, and fermentation of the hydrolysis product to evaluate ethanol yields should help in the... 

Sierra R, Granda CB, Holtzapple MT. (2009). Lime pretreatment. Methods Mol Biol, 581,... 

Chang VS, Nagwani M, Kim CH, Holtzapple MT. (2001). Oxidative lime pretreatment of high-lignin biomass— poplar wood and newspaper. Appl Biochem Biotechnol, 94(1), 1-28. 

Rabelo SC, Filho RM, Costa AC. (2009). Lime pretreatment of sugarcane bagasse for bioethanol production. Appl Biochem Biotechnol, 153, 139-153. 

Sierra, R., Granda, C., Holtzaaple, M.T., 2009. Short-term lime pretreatment of poplar wood. Biotechnology Progress... 

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