[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-197] Effects of heat treatment for the psychrophile-based simple biocatalyst

○Takahisa Tajima¹, Kota Anada¹, Chie Son¹, Akiko Hida¹, Junichi Kato¹ (1. Hiroshima Univ. (Japan))

Keywords:

psychrophile,heat treatment

A psychrophile based simple biocatalyst (PSCat) is an efficient biocatalyst used by the psychrophilic marine bacterium Shewanella sp. as a host microorganism, which cannot grow above 30°C. It can be easily prepared by heat treatment at moderate temperatures (40–50°C) of psychrophilic bacteria expressing mesophilic conversion enzymes. Heat treatment at moderate temperatures inactivates almost all psychrophilic metabolic enzymes that consume substrates and energy materials for by-product formation. Heat treatment also increases the membrane permeability of the substrate by partially disrupting the cell membrane. We constructed an efficient bioconversion process to produce polymer materials using PSCat. It achieved high-yield production of polymer materials such as 3-hydroxypropionaldehyde, 1,3-propanediol, 3-hydroxypropionic acid, aspartic acid, and itaconic acid. Recently, we have focused on the production of aromatic compounds with PSCat. These are also valuable chemicals for engineering polymer materials. PSCat has also been used for sustained reactions by immobilization with alginate because heat treatment disrupts the cell structure and allows leaked conversion enzymes. We observed the cell structures of psychrophilic bacteria after heat treatment using electron microscopy to evaluate the influence of heat treatment at a moderate temperature. After heat treatment, the cells had surface protrusions that caused partial disruption of the cell structure and leakage of cell contents, including conversion enzymes. To evaluate protein leakage from PSCat, we used strains expressing green fluorescent protein (GFP)-fused enzymes to measure leakage from the intensity of GFP fluorescence. Leakage decreased depending on the molecular size of the proteins and the addition of seawater before heat treatment. To determine the factor for decreased protein leakage, inorganic compounds contained in the seawater were added to the cell suspension. Divalent metal ions, Mg²⁺, Mn²⁺, and Zn²⁺, decreased GFP leakage. By optimizing heat treatment conditions and the size of the expressed enzymes, psychrophilic cells can be used repeatedly as biocatalysts for production.