title: Immobilized formaldehyde-metabolizing enzymes from Hansenula polymorpha for removal and control of airborne formaldehyde.
abstract: Formaldehyde (FA)-containing indoor air has a negative effect on human health and should be removed by intensive ventilation or by catalytic conversion to non-toxic products. FA can be oxidized by alcohol oxidase (AOX) taking part in methanol metabolism of methylotrophic yeasts. In the present work, AOX isolated from a Hansenula polymorpha C-105 mutant (gcr1 catX) overproducing this enzyme in glucose medium, was tested for its ability to oxidize airborne FA. A continuous fluidized bed bioreactor (FBBR) was designed to enable an effective bioconversion of airborne FA by AOX or by permeabilized mutant H. polymorpha C-105 cells immobilized in calcium alginate beads. The immobilized AOX having a specific activity of 6-8 U mg⁻¹ protein was shown to preserve 85-90% of the initial activity. The catalytic parameters of the immobilized enzyme were practically the same as for the free enzyme (k(cat)/K(m) was 2.35×10³ M⁻¹ s⁻¹ vs 2.89×10³ M⁻¹ s⁻¹, respectively). The results showed that upon bubbling of air containing from 0.3 up to 18.5 ppm FA through immobilized AOX in the range of 1.3-26.6 U g⁻¹ of the gel resulted in essential decrease of FA concentration in the outlet gas phase (less than 0.02-0.03 ppm, i.e. 10-fold less than the threshold limit value). It was also demonstrated that a FBBR with immobilized permeabilized C-105 cells provided more than 90% elimination of airborne FA. The process was monitored by a specially constructed enzymatic amperometric biosensor based on FA oxidation by NAD+ and glutathione-dependent formaldehyde dehydrogenase from the recombinant H. polymorpha Tf 11-6 strain.
authors.affiliation: Department of Chemical Engineering and Biotechnology, Ariel University Center of Samaria, Ariel 40700, Israel.
authors.forename: Sasi
authors.initials: S
authors.lastname: Sigawi
authors.forename: Oleh
authors.initials: O
authors.lastname: Smutok
authors.forename: Olha
authors.initials: O
authors.lastname: Demkiv
authors.forename: Oksana
authors.initials: O
authors.lastname: Zakalska
authors.forename: Galina
authors.initials: G
authors.lastname: Gayda
authors.forename: Yeshayahu
authors.initials: Y
authors.lastname: Nitzan
authors.forename: Marina
authors.initials: M
authors.lastname: Nisnevitch
authors.forename: Mykhaylo
authors.initials: M
authors.lastname: Gonchar
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000302:isolation & purification* / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D000464:Alginates / Q000737:chemistry; D019149:Bioreactors / Q000382:microbiology*; D015374:Biosensing Techniques; D052918:Environmental Restoration and Remediation; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism*; D005557:Formaldehyde / Q000032:analysis / Q000302:isolation & purification* / Q000378:metabolism; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D007700:Kinetics; D010843:Pichia / Q000201:enzymology*
chemical_list: D000393:Air Pollutants; D000464:Alginates; D004800:Enzymes, Immobilized; D006603:Hexuronic Acids; D005557:Formaldehyde; D020723:Glucuronic Acid; D000429:Alcohol Oxidoreductases; C019643:alcohol oxidase