Microbial contamination in methanol biofilters inoculated with a pure strain of Pichia pastoris: A potential limitation for waste revalorization

Novel biotechnologies to valorize waste emissions are based on the use of specialized microbial groups that produce different compounds of industrial interest. On this scenario, the retention of such specific microorganisms in the system is of critical interest; however, the potential limitations of working with simplified cultures in a competitive open environment are neither fully explored nor well understood. In this work, a series of biofilters treating methanol vapors coupled with heterologous endochitinase production were used to evaluate the performance of a specialized microbial population during a typical open-to-environment operation. The biofilters were inoculated with a transformed strain of Pichia pastoris and were operated identically for about 90 days. The results showed that the biofiltration performance became diverse with time in terms of the elimination capacity (EC) shifting from a variation coefficient of 1.5% (EC = 274 ± 24, 279 ± 5, and 281.9 ± 25 g/m³ h]) at the beginning of the operation to 33% (EC = 297 ± 9, 338 ± 7, and 341 ± 2 g/m³ h]) at the end of operation. Epifluorescence analysis and cloning-sequencing suggested that P. pastoris remained as the dominant microorganism of methanol degradation, whereas diverse airborne bacteria, including Ochrobactrum spp. and Klebsiella oxytoca, played a secondary role possibly associated with the consumption of intermediates. Overall, this study found that low diversity systems operated under non-sterile conditions could be susceptible to contamination with external microorganisms causing a diversifying behavior at the performance and microbial community levels. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2715, 2019