# Bioreactors: Applications and Innovations for a Sustainable and Healthy Future--A Critical Review
## 2 Fundamental Concept Types of bioreactors  
Bioreactors for submerged fermentations (SmFs) and solid-state fermentations (SSFs) have been highlighted in recent years due to the intensification of the use of industrial biotechnological processes, mainly with the popularization of concepts such as biorefineries and bioeconomy, due to the global appeal for processes and sustainable products as well as growth in the production of biopharmaceuticals and vaccines. According to the concepts of Biochemical Engineering, biotechnological processes can occur in a liquid medium (SmF), in a solid medium, with low water activity (SSF), and in the presence or absence of agitation (static and agitated) and aeration (aerated and non-aerated) [3,17]. For submerged fermentations (SmFs) with microbial cells, three types of bioreactors are used, already well known in the literature: the stirred tank (STR), the airlift, and the bubble column bioreactor [3]. According to projections by Procedure Research (2023), the global bioreactors market size was evaluated at 9.3 billion dollars in 2022, and it is expected that over the next 10 years, a growth rate (CAGR) of 12.58% will result in a market size of 30.42 billion dollars by 2032. The main companies producing and selling bioreactors for bench and industrial scales are GE Healthcare (Chicago, IL, USA), Merck KGaA (Darmstadt, Germany), Eppendorf \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Type of Bioreactor** & **Advantages** & **Disadvantages** & **Reference** \\ \hline  & ✓ & Simple design & ✓ & High shear stress, not suitable for \\ Stirred Tank & ✓ & Versatility and scalability & & shear-sensitive cells \\ Reactor (STR) & ✓ & Greater control of & & Complex mechanical agitation system & [1,3,4] \\  & ✓ & Reduced risk of contamination & & \\  & ✓ & Suitable for animal cells—Lower & & \\  & & height/diameter ratio & ✓ & Specific design modifications required \\ Modified STR & ✓ & Reduced shear stress & ✓ & Potentially higher costs & [4] \\  & ✓ & Homogeneous mixture & & \\  & ✓ & High mass transfer & ✓ & Difficult to scale up \\ Airlift bioreactor & ✓ & Good mixing with low-shear stress & ✓ & Limited use compared to STR in & [3,5] \\  & ✓ & Low energy consumption & & industrial settings \\  & ✓ & Easy operation in sterile conditions & & \\  & ✓ & High mass transfer–Low shear stress & ✓ & Difficult to scale up \\ Bubble Column & ✓ & Low energy consumption & ✓ & Limited use compared to STR & [3,6] \\ Bioreactor & ✓ & Simple design & ✓ & Limited scale expansion (up to 500 L) \\  & ✓ & No need for sterilization (disposable) & ✓ & Limited scale expansion (up to 500 L) \\ Wave Bioreactor & ✓ & Suitable for low oxygen demand cells & ✓ & Not suitable for high & [7,8] \\  & ✓ & Simple configuration & & oxygen-demanding crops \\  & ✓ & Eliminates the need for cleaning & & \\  & & and sterilization & & \\ Disposable & ✓ & Reduces contamination risk & ✓ & Environmental concerns (plastic waste) \\ Bioreactor & ✓ & Flexible and efficient & ✓ & Potentially higher long-term costs & [9,10] \\  & ✓ & Suitable for various scales & & \\  & ✓ & Efficient separation & ✓ & High costs \\ Membrane & ✓ & Continuous operation & ✓ & Complex maintenance & [11,12] \\ Bioreactor (MB) & ✓ & Contamination control & ✓ & Flow limitations \\  & ✓ & Space saving & ✓ & Damage to filamentous fungi \\  & ✓ & Suitable for low water activity media & ✓ & Uneven biomass growth \\ Solid-State & ✓ & Can use various substrates—Less & ✓ & Issues with aeration/heat & [13] \\ Fermentation & & energy intensive & & transfer—inoculation and \\  & & & sterilization challenges & \\
3D-Printed & ✓ & Customizable design & & \\  & ✓ & Efficient process optimization & & High initial setup cost, complexity in & [14, 15, 16] \\ Bioreactor & ✓ & Application in various bioprocesses & & design and manufacturing & [14, 15, 16] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Types, advantages, and disadvantages of bioreactors.