Effect of liquid hot water pretreatment on selected properties of rice husk and its particleboard

Rice husk has a water repellent wax layer on its surface and has high pH and buffering capacity, which inhibit surface adhesion and result in the poor strength and water resistance of rice husk particleboard bonded with water-borne urea formaldehyde (UF) resin. In this work, rice husks were pretreated with liquid hot water at different temperatures (130, 140, 150, and 160 °C) and residence times (10 and 20 min). Pretreated rice husks were used to produce particleboard with UF resin. The effects of liquid hot water pretreatment temperature and residence time on the wax contents and pH values were investigated. In addition, the buffering capacities of the rice husks and the mechanical properties and the water resistance of the rice husk particleboards were investigated. The results indicated that liquid hot water pretreatment remarkably reduced the wax contents, pH values, and buffering capacities of the rice husks. In addition, it improved the mechanical properties and water resistance of the rice husk particleboards. Liquid hot water pretreatment effectively improved bondability between rice husks and water-borne UF resin, and it enhanced the performance of the rice husk particleboard.

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Liquid Hot Water Pretreatment and Enzymatic Hydrolysis as a Valorization Route of Italian Green Pepper Waste to Delivery Free Sugars

Foods ◽

10.3390/foods9111640 ◽

2020 ◽

Vol 9 (11) ◽

pp. 1640

Author(s):

M.A. Martín-Lara ◽

L. Chica-Redecillas ◽

A. Pérez ◽

G. Blázquez ◽

G. Garcia-Garcia ◽

...

Keyword(s):

Enzymatic Hydrolysis ◽

Liquid Fraction ◽

Hot Water ◽

Effect Of Temperature ◽

Green Pepper ◽

Free Sugars ◽

Liquid Hot Water Pretreatment ◽

Liquid Hot Water ◽

Water Pretreatment ◽

Hot Water Pretreatment

In this work, liquid hot water pretreatment (autohydrolysis) was used to improve enzymatic hydrolysis of a commonly consumed vegetable waste in Spain, Italian green pepper, to finally produce fermentable sugars. Firstly, the effect of temperature and contact time on sugar recovery during pretreatment (in insoluble solid and liquid fraction) was studied in detail. Then, enzymatic hydrolysis using commercial cellulase was performed with the insoluble solid resulting from pretreatment. The objective was to compare results with and without pretreatment. The results showed that the pretreatment step was effective to facilitate the sugars release in enzymatic hydrolysis, increasing the global sugar yield. This was especially notable when pretreatment was carried out at 180 °C for 40 min for glucose yields. In these conditions a global glucose yield of 61.02% was obtained. In addition, very low concentrations of phenolic compounds (ranging from 69.12 to 82.24 mg/L) were found in the liquid fraction from enzymatic hydrolysis, decreasing the possibility of fermentation inhibition produced by these components. Results showed that Italian green pepper is an interesting feedstock to obtain free sugars and prevent the enormous quantity of this food waste discarded annually.

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