Provided are an immobilized enzyme and an application thereof in continuous production. The immobilized enzyme is a Polyethyleneimine (PEI)-modified immobilized enzyme, and includes: an enzyme, which includes Amine Dehydrogenase (AmDH) and/or Formate Dehydrogenase (FDH); and a carrier, which is a cyanuric chloride-activated amino carrier. The problem in the prior art of poor performance of an immobilized enzyme is solved, the catalytic activity and reusability of the immobilized enzyme are improved, and the immobilized enzyme is suitable for the field of enzyme immobilization.

Provided herein are methods, compositions, and non-naturally occurring microbial organism for preparing compounds such as 1-butanol, butyric acid, succinic acid, 1,4-butanediol, 1-pentanol, pentanoic acid, glutaric acid, 1,5-pentanediol, 1-hexanol, hexanoic acid, adipic acid, 1,6-hexanediol, 6-hydroxy hexanoic acid, -Caprolactone, 6-amino-hexanoic acid, -Caprolactam, hexamethylenediamine, linear fatty acids and linear fatty alcohols that are between 7-25 carbons long, linear alkanes and linear -alkenes that are between 6-24 carbons long, sebacic acid and dodecanedioic acid comprising: a) converting a C.sub.N aldehyde and pyruvate to a C.sub.N+3 -hydroxyketone intermediate through an aldol addition; and b) converting the C.sub.N+3-hydroxyketone intermediate to the compounds through enzymatic steps, or a combination of enzymatic and chemical steps.

The polypeptide comprises a sequence having 90% or higher sequence identity to an amino acid sequence represented by SEQ ID NO: 1 with one amino acid residue thereof engineered, and has higher catalytic activity for the reductive amination reaction between at least one compound A represented by the formula (1) or a salt thereof and at least one compound B represented by the formula (2) or a salt thereof or the intramolecular reductive amination reaction of at least one compound B or a salt thereof than that of a polypeptide comprising the amino acid sequence represented by SEQ ID NO: 1 under at least one reaction condition.

One aspect of the present invention relates to a method for producing an amino acid, comprising a step of performing the following reaction (i) or (ii) in the presence of a polypeptide comprising an amino acid sequence having 90% or higher identity to an amino acid sequence represented by SEQ ID NO: 1, a reducing agent, and compound D represented by the following formula (1): (i) an intermolecular reductive amination reaction between compound A selected from the group consisting of a compound having an amino group and a salt thereof and compound B selected from the group consisting of a compound having a carbonyl group and a salt thereof; (ii) an intramolecular reductive amination reaction of compound C selected from the group consisting of a compound having an amino group and a carbonyl group and a salt thereof.

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