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

Abstract

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

Biofiltration of high concentrations of methanol vapors: removal performance, carbon balance and microbial and fly populations

“…Nevertheless, little is known about biofiltration limits, particularly regarding steady state operation at the maximum system capacity under high concentrations of methanol. As can be seen in Table , most studies have focused on the treatment of inlet methanol concentrations ( C in ) below 5 g m −3 , while only three experiments have reported results above 10 g m −3 . Actually, among those three studies, only one (with different aspects reported in two references), truly reflects the biological degradation of methanol during steady state operation .…”

“…As can be seen in Table , most studies have focused on the treatment of inlet methanol concentrations ( C in ) below 5 g m −3 , while only three experiments have reported results above 10 g m −3 . Actually, among those three studies, only one (with different aspects reported in two references), truly reflects the biological degradation of methanol during steady state operation . In one of the other studies, as reported by the authors, high methanol concentrations were only applied as part of a shock‐load test, without mirroring biofilter performance under extended high loads .…”

“…Biological oxidation of methanol vapors has been successfully applied in biofilters or biotrickling filters (similar to the precedents, but with continuous recirculation of a mineral medium solution across the filter bed), with various types of packing materials, operating conditions and microbial populations (Table ) . Nevertheless, little is known about biofiltration limits, particularly regarding steady state operation at the maximum system capacity under high concentrations of methanol.…”

Proof of concept of a novel in tandem biofilter photobioreactor system for valorization of volatile organic compounds: mineralization of methanol vapors coupled with use of CO2 as a carbon source for Arthrospira maxima growth

“…Biofilter biomass has been considered a first valorization option, mostly via protein production, particularly in the case of alcohol vapor treatment 3,4 . However, in situ biomass valorization is hindered by microbial contamination, as biofilter populations evolve 5 . The exploitation of CO 2 , the main carbon endpoint of VOC biofiltration, 6 could be a worthy alternative.…”

“…3,4 However, in situ biomass valorization is hindered by microbial contamination, as biofilter populations evolve. 5 The exploitation of CO 2 , the main carbon endpoint of VOC biofiltration, 6 could be a worthy alternative. Biological valorization of CO 2 biofilter emissions has never been attempted and, in such a context, photosynthetic technologies seem to be particularly convenient.…”