Fig 5.

Enzymatic activity in supernatants of cocultures producing the cellulase and the xylanase. The substrate was pretreated wheat straw, and the measured activities are compared with the corresponding theoretical additive effect. Cells were inoculated using various ratios (Cel6A/Xyn11A): 1:500, 1:100, 1:50, 1:10, 1:1, 10:1, 50:1, 100:1, and 500:1 (where the 10:1 cell ratio corresponds to an approximate 1:1 molar ratio of the secreted enzymes, since cellulase production is approximately 10-fold lower; see the text and Fig. 3). The concentration of pretreated wheat straw (dry matter) in the reactions was 3.5 g/liter. Assuming that all detected reducing ends belong to dimers, the highest detected product concentration (1:500 ratio) represents 27.6% polysaccharide conversion. Enzymatic activity is defined as mM soluble reducing sugars following a 24-h reaction period at 37°C and pH 5. Each reaction was performed in triplicate, and standard deviations are indicated. The theoretical additive effect is defined as the sum of the activities of the individual Cel6A- and Xyn11A-secreting cultures (see Materials and Methods for a detailed explanation), and synergism was calculated as the ratio between the measured activity and the theoretical activity, assuming additivity.