Effect of the SP20 module on the secretion efficiency of MHETase and PETase. (a) Level 2 MoClo constructs harboring the aadA selection marker, and the coding sequences for MUT-PETase and MHETase equipped with the secretion signals (BBa_K3002212, BBa_K3002213, BBa_K3002214) introduced in Figure 6 and a C-terminal SP20 tag for enhancing glycosylation. See Figure 1 for the description of other parts. (b) UVM4 transformants containing the constructs shown in (a) were grown in TAP medium for seven days. Cells were centrifuged and the supernatant lyophilized, resuspended in 2xSDS buffer and analyzed by SDS-PAGE and immunoblotting with an anti-HA antibody. Transformants C12 (BBa_K3002202) and A27 (BBa_K3002200) introduced in Figures 4 and 5, respectively, served as positive controls. The black arrow points to MHETase, the white arrow to MUT-PETase.

The SP20 module increases the efficiency of protein secretion. (a) Level 2 MoClo constructs harboring the aadA selection marker, and the coding sequences for MUT-PETase and MHETase equipped with the secretion signals introduced in Figure 6. The constructs contain the coding sequence for a conventional 3xHA tag (C, K, L)(BBa_K3002202, BBa_K3002210, BBa_K3002211), or the 3xHA tag preceded by a SP20 tag to enhance glycosylation (M, N, O). See Figure 1 for the description of other parts. (b) UVM4 transformants containing the constructs C, K, L and M, N, O (BBa_K3002202, BBa_K3002210, BBa_K3002211, BBa_K3002212, BBa_K3002213, BBa_K3002214) were grown in TAP medium for seven days. Cells were centrifuged and the supernatant lyophilized, resuspended in 2xSDS buffer and analyzed by SDS-PAGE and immunoblotting with an anti-HA antibody. Transformant A27 introduced in Figures 4, served as positive control. The black arrow points to MHETase, the white arrow to MUT-PETase and the grey arrow to RPL1 (chloroplast ribosomal 50S protein L1). The RPL1 antibody was used to detect contamination from intracellular proteins.

Verification of secretion of MHETase and MUT-PETase into the medium. Transformants generated with constructs M, N, and O (BBa_K3002212, BBa_K3002213, BBa_K3002214)(Figure 8) were grown in TAP medium for seven days. Cells were centrifuged and the supernatant (s) lyophilized and resuspended in 2xSDS buffer. Cell pellets (p) were also resuspended in SDS-buffer. Both fractions were analyzed by SDS-PAGE and immunoblotting with an anti-HA antibody. The black arrow points to MHETase, the white arrow to MUT-PETase.

Quantification of secreted MHETase and MUT-PETase. (a) Transformants generated with constructs C, J, M, N, and O (BBa_K3002202, BBa_K3002208, BBa_K3002212, BBa_K3002213, BBa_K3002214)(Figure 8) were grown in TAP medium for seven days. Cells were centrifuged and the supernatant lyophilized, resuspended in 2xSDS buffer and analyzed by SDS-PAGE and immunoblotting with an anti-HA antibody. Whole-cell extracts of strain B1-TIG-HA for which concentrations of the HA-tagged TIG protein are known are loaded next to the lyophilized supernatants. The black arrow points to MHETase, the white arrows to MUT-PETase. The supernatant of a culture with the UVM4 strain were loaded as negative control. (b) Maximum cell densities, doubling times, daily growth rates, yields of MHETase and PETase and daily productivity of both combined were calculated for the transformant lines indicated.