A Study of The Effect of The Particle Size of Barley and Wheat Straw During Enzyme Hydrolysis to Produce Fermentable Sugars

Agricultural waste presents an attractive source for bioethanol production, with the most important and energy-consuming step being the pre-treatment process. Barley and wheat straw are some of the best feedstocks for... [ view full abstract ]

Agricultural waste presents an attractive source for bioethanol production, with the most important and energy-consuming step being the pre-treatment process.

Barley and wheat straw are some of the best feedstocks for bio-ethanol production due to their low price, available and relatively high sugar yield.

The aim of this paper is to study the effect of particle size on the total sugar yield during hydrolysis from barley and wheat straw. Firstly the barley and wheat straw was subjected to physical-treatment by using (Komo) grinder, the raw material was ground with different gaps between the ceramic disks and then passed through sieves to achieve different particle sizes of >2000 µm,  2000-1000 µm, 1000-710 µm, 710-500 µm, 500-250 µm and <250 µm. The hydrolysis was the performed by using Celluclast 1.5L from T. reeseiand Novozyme 188 (ẞ-Glucosidase) from Aspergillus enzymes. The hydrolysis was carried at 50°C and 200 rpm in a incubate shaker using 50 ml of sodium citrate buffer at pH 4.8 for 72 hr. Samples were taken every 24 hr such that a sugar yield test could be carried out by the DNS method using (UV) spectrophotometer.  Further tests were then carried out for the most successful conditions using gas chromatography-mass spectrometry (GC-MS) to get the sugar compositions. The maximum sugar yield was achieved by hydrolysis of the >250 µm samples for both barley and wheat straw. The total sugar yield was 8.1 (g/l) and 7 (g/l) for barley and wheat straw, respectively. As shown in Figure 1, the results illustrated that smaller particle size gave higher sugar yield and it shows a promising sugar yield without using any chemicals or further treatment steps especially for barley straw. However, there needs to be further improvements to the process and the energy consumption needs to be reduced.