Fermentation 101 – Bioprocess Development, Optimization & Scale-up
Increasing demand for biologicals has put fermentation at the forefront of biotechnology, and consequently, fermentation capacities are increasing globally. However, making fermentation a competitive solution is not just about building new and bigger facilities. It is also about fermenting better, which requires a deep understanding of the target microbe, how to grow it, and how to get the most out of it while minimizing costs.
Bioprocess development and optimization are critical in scaling and delivering economically viable biologicals. To understand why and how, let’s explore the core elements, challenges, and strategies for successfully developing a microbial fermentation process.
Differences Between Production Scales (Lab, Bench, Pilot, Industrial)
The journey of a microbial fermentation process development typically begins at the lab scale, where shake flasks or small bioreactors (1–2 liters) are used to test strains, media, and process parameters (temperature, pH, oxygen levels, etc.). The primary goal at this stage is to collect enough information to guide subsequent trials and validate the suitability of selected process parameters. With this data, the process moves to the bench scale (typically 5–50 liters), where production is further optimized.
The pilot scale (100–1,000 liters) is an intermediate step between bench and industrial scales, where the feasibility of the process is validated for commercial production. Finally, at the industrial scale (>1,000 liters), the bioprocess is optimized for large-scale volumes, with additional considerations for cost efficiency, stability, and sustainability.
Key Elements of Bioprocess Development
Every fermentation process has three base components – target microbe(s), substrate, and the environment (production parameters). Bioprocess development must address each of these components to maximize the yield and streamline downstream processing of the microbial biomass.
1. Microbe
Everything begins with the target microbe – the most promising microbial candidates are selected, and information about their biology, biochemical activity, and growing requirements is used as a foundation for the whole production endeavor and subsequent bioprocess optimization.
2. Substrate
Substrate choice is one of the most critical factors in bioprocess development. Its role is to provide key nutrients, physical support to microbial colonies, and effective control of production parameters. Different microbes can have vastly different demands when it comes to the nutritional and physical qualities of the substrate, so a tailored approach is often necessary.
3. Environment (Production parameters)
Maintaining the right set of environmental conditions for the growth of the targeted microbe is crucial for achieving the desired product quality and quantity. The key conditions, or production parameters, include temperature, pH, aeration (dissolved oxygen), and nutrient concentration. Fine-tuning these parameters and maintaining them throughout the entire production process is one of the key challenges of bioprocess development.
Yield
Yield is the key determinant of the economic viability of any fermentation process. Maximizing yields and minimizing costs, while maintaining high product quality is the end goal of every bioprocess development endeavor. Yield directly impacts the cost per unit of the final product, making yield optimization a priority in the early stages of bioprocess development.
Downstream processing
Last but not least, downstream processing is the critical step in converting the raw microbial biomass into a product that meets commercial requirements. It includes a series of procedures to separate the substrate from the biomass (in the case of solid substrates), extract the desired active ingredient, and formulate it according to the target application. Special considerations during this step include minimizing the loss of viable cells during processing, application route (final formulation), and maximizing the shelf life of the end product.
Producing Better – Bioprocess Optimization
Bioprocess optimization is aimed at maximizing the key quality attributes of the end product – purity, potency, and stability – with economics in mind. These quality attributes are highly dependent on the previously mentioned key elements, and consequently, these elements are the main targets for optimization – specifically the substrate, yield, and downstream processing.
Optimizing Substrate
Optimizing the fermentation substrate can significantly increase the productivity and quality of the microbial biomass while lowering costs. There are different approaches depending on the type of substrate (liquid, solid), equipment used (bioreactor type), and downstream processing requirements.
The key considerations in substrate optimization include reducing contamination risks, ensuring optimal nutrient distribution, and making downstream processing as simple and efficient as possible. Another important consideration is the reduction of costs, which can be quite high for certain raw materials, especially at larger scales.
Optimizing Yield
Maximizing microbial yield is essential for a successful fermentation process. Optimization strategies are mostly focused on fine-tuning the production parameters – temperature, pH, oxygen transfer rates, and nutrient levels. The vast variability of microbes and their growing requirements, along with sometimes very subtle differences between a success and a failure, create a need for consistent monitoring and a high level of process control.
Analytics – Monitoring & Control
Effective monitoring and control of production parameters can make or break the entire fermentation endeavor. Knowing what is going on in the fermentation tank at every step of the way significantly reduces the risk of undesired outcomes. Modern analytical solutions offer real-time monitoring of dissolved oxygen, pH, and microbial density, enabling more precise control over production parameters. Advanced analytical and machine learning tools can also be employed to predict potential process issues and facilitate timely adjustments to avoid failed batches.
Optimizing Downstream Processing
The main concerns in downstream processing are maintaining microbial cell viability during biomass processing and ensuring the long-term stability of the final product. Even the best microbes, most effective enzymes, and other high-performing biologicals can fail to deliver the desired effects if they are not equipped with the right tools to meet the requirements of the target application. Long-term viability – shelf-life – plays a critical role in market adoption and product performance, and formulation approaches aimed to extend it are the prime targets for optimization.
Producing More – Bioprocess Scale-Up
Scaling up a bioprocess isn’t a simple linear function, as different production scales come with different technical challenges. What works at the lab scale is usually far from optimal at larger scales, where even the slightest deviation can be very costly. Key considerations revolve around process consistency, microbial behavior, and bioreactor design.
Technical Challenges and Solutions
From Shake Flask to Bioreactor: In small-scale shake flasks, conditions such as oxygen transfer, agitation, and heat dissipation are easy to track and maintain. However, these parameters become difficult to control in larger bioreactors. Bioreactor design is key here, as it provides the foundation for the environment in which the microbes will grow, and it must ensure efficient oxygen and nutrient distribution, as well as temperature and pH control.
From Lab Scale to Pilot-Industrial Scale: At the lab scale, it is easier to successfully produce various microbial strains and get the desired product quality, as the production process is easier to monitor, adapt, and control. However, as fermentation is scaled to pilot and industrial scales, the process must be robust enough to accommodate the increased volume, while maintaining consistent microbial growth and product quality. Things change at larger volumes, and the error margin is significantly lower. Consistent, real-time monitoring and analytics play an increasingly important role as the scales go up, providing insights into what is going on in the tank, predicting microbial behavior, and enabling early detection of potential problems.
How to Achieve a Successful Scale-Up?
Achieving a successful scaleup is not just about the technicalities – target microbe, bioprocess development, optimization, cutting-edge equipment, and analytics – it is also about communication and knowledge transfer. The development of biological products from lab to industrial scale involves the collaboration of multiple players (academic institutions, CDMOs, CMOs, etc.), making knowledge transfer critical for a successful scale-up. Minimizing the loss of information during this process is the first, and probably the most important step in setting a foundation for productive and cost-efficient microbial production.
Takeaway
Advancing a bioprocess from lab to industrial scale requires a comprehensive approach that includes bioprocess development, optimization, and scale-up, with a high focus on productivity and cost reduction. From selecting the right substrate to optimizing microbial yields and coming up with more effective formulations, each stage plays a vital role in the success of a microbial fermentation endeavor. As bioprocess technology continues to evolve, more efficient and scalable fermentation methods will pave the way for higher yields, better product quality, and more sustainable industrial production.
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