The phrase "act as substitute" is correct and usable in written English.
It can be used when referring to someone or something that takes the place of another in a specific role or function.
Example: "In the absence of the regular teacher, I will act as substitute for the day."
Alternatives: "serve as a replacement" or "function as an alternative".
If, like us, the crowds put you off going to the Tower to see the poppies, then perhaps The Passing Bells (BBC1) can act as substitute.
According to Ulrich Mellinghof, head of safety development at the brand, the tunnels are not intended to act as substitute environments for road testing, but should allow the automaker to test certain features in prototype and then select the top-performing equipment for subsequent road tests.
Moreover, aptamers that are specific antagonists of protein function can act as substitute interaction partners in HTS assays to facilitate the identification of small-molecule lead compounds.
The possible gridlock caused by its lack of an absolute majority in the Senate could be the catalyst for discussing the possibility of a non-partisan political figure to act as substitute president for the next four years.
Family members are often required to act as substitute decision-makers when health care or research participation decisions must be made for an incapacitated relative.
On the other hand, these products may act as substitutes for long-acting insulin analogues and thus reduce the daily dose of DET and GLAR.
In the absence of reputation, the government and regulators act as substitutes to ensure appropriate conduct.
Animal blood or rare steaks may act as substitutes, but for most vampires nothing beats fresh blood.
We have to act as substitutes for handling their asylum applications, giving them psychological support, and finding solutions to improve their living conditions," said Carlo Cominelli, head of the K-Pax co-operative.
More than half of the members teach at leading conservatories or universities, and some of their students act as substitutes, but that has periodically led to quality-control problems.
As previous ALMPs, training measures can act as substitutes for work experience (screening effect)144.
