The Effect of Enzyme Addition on the Anaerobic Digestion …
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lipase addition on the physiochemical properties of the food waste digestate and the
biogas production were also investigated.
2 Materials and Methods
2.1 Food Waste, Inoculum and Enzyme
Food waste was collected from a cafeteria in the Faculty of Engineering (FKJ), Universiti Malaysia Sabah, Kota Kinabalu, Sabah. The collected food waste was sealed
and stored in laboratory for further use. Inoculum was prepared through 51 days
anaerobic digestion of food waste. The Candida Antartica lipase B Lipozyme (CALB
L) used was purchased from Novozyme Inc. (Davis, CA) and was selected based on
its ability to hydrolyse high fat content substrate.
2.2 Anaerobic Digestion of Food Waste
The anaerobic digestion process was carried out by feeding 350 g of food waste
into a 500 mL bottle as a batch reactor. The amount of lipase used was 0.015 g
lipase/100 g of food waste. Control reactors without enzyme were also prepared.
All reactors were sealed for 40 days. For each consecutive 10 days, the sample of
food waste was collected for physiochemical analysis. The biogas produced from
the anaerobic digestion process was collected using the water displacement method.
All experiments were done in duplicates.
2.3 Physiochemical Analysis
The food waste samples for days 0, 10, 20, 30 and 40 were analysed for pH, conductivity, moisture content and Total Organic Carbon (TOC). All analysis methods and
calculation were adapted from Yaser et al. (2007).
2.3.1 Total Organic Carbon (TOC)
The samples were oven dried at 105 °C for 24 h. The dried samples were burned in
the furnace at 550 °C for 4 h. The organic matter was determined as volatile solid.
The percentage of TOC was determined by using Eq. 2.1.
121
lipase addition on the physiochemical properties of the food waste digestate and the
biogas production were also investigated.
2 Materials and Methods
2.1 Food Waste, Inoculum and Enzyme
Food waste was collected from a cafeteria in the Faculty of Engineering (FKJ), Universiti Malaysia Sabah, Kota Kinabalu, Sabah. The collected food waste was sealed
and stored in laboratory for further use. Inoculum was prepared through 51 days
anaerobic digestion of food waste. The Candida Antartica lipase B Lipozyme (CALB
L) used was purchased from Novozyme Inc. (Davis, CA) and was selected based on
its ability to hydrolyse high fat content substrate.
2.2 Anaerobic Digestion of Food Waste
The anaerobic digestion process was carried out by feeding 350 g of food waste
into a 500 mL bottle as a batch reactor. The amount of lipase used was 0.015 g
lipase/100 g of food waste. Control reactors without enzyme were also prepared.
All reactors were sealed for 40 days. For each consecutive 10 days, the sample of
food waste was collected for physiochemical analysis. The biogas produced from
the anaerobic digestion process was collected using the water displacement method.
All experiments were done in duplicates.
2.3 Physiochemical Analysis
The food waste samples for days 0, 10, 20, 30 and 40 were analysed for pH, conductivity, moisture content and Total Organic Carbon (TOC). All analysis methods and
calculation were adapted from Yaser et al. (2007).
2.3.1 Total Organic Carbon (TOC)
The samples were oven dried at 105 °C for 24 h. The dried samples were burned in
the furnace at 550 °C for 4 h. The organic matter was determined as volatile solid.
The percentage of TOC was determined by using Eq. 2.1.