Annually, the oil and gas industry faces equipment losses and product quality degradation due to the presence of
sulfate-reducing bacteria (SRB). Given the negative impact of SRB, this study evaluates the use of photoinactivation
(PI) with zinc chloride double salt of 1,9-Dimethyl-Methylene Blue (DMMB) as a photosensitizer
(PS) in varying concentrations and combined with Laser light at different exposures in an SRB consortium. For
culture growth, a modified Postgate C medium (without ferrous sulfate) was used, and cell quantification was
performed on 100 μL aliquots of the consortium, read on a spectrophotometer (λ600 nm) in an oxygen- and lightfree
environment at room temperature. Statistical analyses included two-way ANOVA and ANOVA with interaction
to separately and jointly evaluate the effects of PS and light in PI. Results indicated microbial activity in all
groups, with an antimicrobial inhibition rate exceeding 50 % (p < 0.05) for concentrations above 1.5 μg/mL of
DMMB. PI efficacy significantly depended on DMMB concentration and light density, achieving a 70.58 %
(55.73–70.58, with a mean of 66.71 %) reduction (p < 0.05) with 1.5 μg/mL of DMMB and a 70.15 % (65–70.15,
with a mean of 68.21 %) reduction with 2.0 μg/mL at an intensity of 21.6 J/cm2. In conclusion, PI presents a
promising alternative to biocides in the oil and gas industry, offering easy application, avoiding bacterial
resistance, being environmentally safe, and compatible with other SRB population control techniques.
