The waste fines (WF) rejected by paper mill are one of the good resources of lignocellulosic biomass to produce sugars. The potential of hydrolysis yield was around 95% (reducing sugars g/g of digestible fibers). The inhibitory effects of the substrate were studied since the enzyme demand for the hydrolysis was not economically feasible.
The major inhibitor of WF was the high portion of ash for enzymatic hydrolysis. The CaCO3 among the ash was the strongest inhibitor with three different inhibiting effects. The first inhibition was related to reduced free enzyme in bulk solution resulted by non-productive enzyme adsorption on CaCO3. The binding mechanism could be explained by the electrostatic and hydrogen bonding interaction between the enzyme and CaCO3. The major mechanism of the enzyme – CaCO3 binding differ with the enzyme – lignin binding which has been reported that the hydrophobic interaction is the major mechanism for the enzyme – lignin binding. The different mechanisms are due to the hydrophobic property: CaCO3 is hydrophilic and lignin is hydrophobic. The application of a nonionic surfactant, Tween 80, could be a solution to free enzyme in bulk solution via competitive bond on CaCO3 with a higher affinity than the enzyme. A study of CaCO3 of particle size and Tween 80 adsorption on CaCO 3 provided evidence of this Tween 80 effect. The second inhibiting effect of CaCO3 was pH level shift decreasing enzyme activity by dissolved Ca2+. pH adjustment (PAD) was tested with addition of acids to make the pH optimum for enzyme activity. PAD with extra acetic acid resulted in a positive effect but sulfuric acid did not improved hydrolysis yields. The combination application of Tween 80 and PAD yielded more than two times as much sugar release compared to the non-treated waste fines with a 10 FPU enzyme dose. The final inhibitory effect of CaCO3 was dissolved Ca2+ reduced of enzyme activity. This effect was supported by the reduction of hydrolysis yield of Avicel and unbleached kraft pulp (UKP), and documentation of particle size increase due to the aggregation of enzyme in the presence of Ca2+.
Some other approaches were studied to improve the hydrolysis yield of paper mill waste fines. These included using combinations of adding nonionic surfactant, high consistency hydrolysis, buffer substitution, and deinking flotation. Each method improved the productivity or reduced the cost of production and may be combined in one process to get synergetic effects.
|Advisor:||Ramarao, Bandaru V.|
|Commitee:||Amidon, Thomas E., Bujanovic, Biljana, Doelle, Klaus, Leopold, Donald J., Liu, Shijie|
|School:||State University of New York College of Environmental Science and Forestry|
|Department:||Paper and Bioprocess Engineering|
|School Location:||United States -- New York|
|Source:||DAI-B 78/10(E), Dissertation Abstracts International|
|Subjects:||Chemical engineering, Wood sciences, Environmental engineering|
|Keywords:||Buffer substitution, Calcium carbonate, Enzymatic hydrolysis, Paper mill waste, Ph adjustment, Surfactant|
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