Optimising the (Microwave) Hydrothermal Pretreatment of Brewers Spent Grains for Bioethanol Production

Table 3

Experimental design used to simultaneously evaluate the impacts of variation of the % solids loading and reaction time during microwave based autohydrolytical pretreatment of BSG at 200°C according to a D-optimal design space. Autohydrolytical pretreatment utilized a Monowave 300 microwave synthesis reactor with G30 vessels (Anton Parr).

Run	Factor 1	Factor 2
	A: solids loading	B: time
	% (w/v)	(min)
1	35	5
2	10	10
3	22.5	10
4	22.5	5
5	35	15
6	10	5
7	10	15
8	35	15
9	35	5
10	22.5	10
11	22.5	15
12	22.5	10
13	35	10
14	10	5
15	16	7.5
16	29	7.5
17	16	12.5
18	29	12.5
19	10	15

D-optimal experimental design created using DesignExpert (Stat-Ease, USA) using a collection of reaction combinations (temperatures and times) from which the D-optimal algorithm chose the treatment combinations to include in the design. This reduced the total number of experiments needed to be conducted from that of a full factorial experimental design.