<![CDATA[Biotechnology frequently employs Escherichia coli to produce recombinant proteins. However, its efficiency is strongly influenced by induction conditions, particularly the quantity of isopropyl ?-D-1-thiogalactopyranoside (IPTG). This study aimed to evaluate the effect of different IPTG concentrations on the expression of recombinant Jembrana Superficial Unit (JSU) protein in E. coli BL21. The JSU gene cloned into the pET21a vector was induced at 37°C for 1 hour using three IPTG concentrations (0.3, 0.6, and 0.9 mM), each performed in triplicate. SDS-PAGE analysis confirmed successful expression of the recombinant JSU protein, indicated by a distinct band at approximately 37 kDa, consistent with its predicted molecular weight. Bacterial cells were lysed by freeze–thaw, and protein expression levels were quantified by spectrophotometry from optical density measurements and expressed in arbitrary units. Statistical analysis using one-way ANOVA, following confirmation of data normality and homogeneity of variance, revealed mean expression levels of 1.69 ± 0.15, 1.59 ± 0.11, and 1.76 ± 0.28 a.u. for 0.3, 0.6, and 0.9 mM IPTG, respectively, indicating a non-linear trend with a modest increase at the highest concentration. Nevertheless, there were no statistically significant differences between the treatments (p>0.05). These findings suggest that, within the tested range, variation in IPTG concentration does not significantly influence JSU protein expression under the applied conditions. Further optimisation, including a broader range of inducer concentrations and induction durations, is recommended to enhance the production of soluble, functional JSU protein.]]>
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