Newsprint, hydrolysis

Figure 8 is a schematic flow diagram for the hydrolysis of waste newsprint. Most of the process design criteria and the economic evaluations of the saccharification process have been based on newsprint as substrate. Notable analyses are those of Wilke and co-workers (21) and Humphrey (22). In the hydrolysis, the substrate is first pretreated (milling), to make it more accessible to the enzyme. Saccharification takes place in a reaction vessel, where the substrate is contacted with the enzyme solution from the fermentation vessel. Glucose solution is separated from unreacted substrate at the outlet of the vessel and the solution passes on to a concentration stage before the sugar is used in the yeast fermentation to produce alcohol. 

In a typical enzymatic hydrolysis of a 5% suspension of ball-milled newsprint, a sugar syrup containing 1.6% glucose, 1.4% cellobiose, and 0.2% xylose is readily obtained. Figure 3 is illustrative of kinetic results obtained with T. viride cellulase at 3.5-filter-paper-units/mL (FP units/ mL) strength in a 5% suspension of ball-milled newsprint. 

Results with newsprint are roughly intermediate between those for wood and cotton linters. Hydrolysis of the delignified chemical pulp component (about 20% of the total newsprint furnish) and of the accessible carbohydrates of the groundwood component is accomplished with about 4 days of digestion. Further hydrolysis of the groundwood carbohydrate is then stymied by lignin as in the case of red oak and Douglas fir. 

Inspection of the data in Table IV shows that fine grinding causes a substantial increase in the rates of hydrolysis of all four substrates— nearly nine-fold for cotton linters and about five-fold for newsprint and Douglas fir after 120 min of milling. Red oak is somewhat less responsive, requiring 240 min of milling for a five-fold rate increase. 

The relative influence of vibratory milling on the course of enzymatic and dilute acid hydrolysis of four cellulosic substrates was investigated. The four substrates—cotton linters, newsprint, Douglas fir, and red oak— were vacuum-dried and then milled for various time periods ranging up to 240 min. Assays were then made of rate and extent of hydrolysis, maximum yield of reducing sugar, and cellulose crystallinity. 

Duff SJ, Moritz JW, Casavant TE. Effect of surfactant and particle size reduction on hydrolysis of deinking sludge and nonrecyclable newsprint. Bio-technol Bioeng 1995 45 239-244. 

Grethlein, H., Comparison of the economics of acid and enzymatic hydrolysis of newsprint. Biotechnology and Bioengineering 1978, 20, 503-525. 

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... 

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