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Inefficiency and waste in the fermentation process can pose problems for meat substitute manufacturers. And these problems are unwelcome for businesses who wish to scale up production. Mark Richardson, processing product manager of Parker Bioscience Filtration, explores the solutions.

From vegan mince to ‘fake’ bacon, more and more meat substitute products are appearing on supermarket shelves.

As an increasing number of consumers switch to vegan diets or reduce the number of animal products on their shopping lists, the global meat substitute market is growing.

According to Custom Market Insights, the global meat substitute market size was expected to reach a valuation of $10.1 billion in 2023 and is anticipated to reach a valuation of $233.87 billion by 2030 at a CAGR of 42.1% from 2023 to 2030.

However, manufacturers will need to scale up production as demand grows. They will also need to operate more efficiently in an increasingly competitive market.

In addition, manufacturers are also under pressure from rising energy costs. Combine this with the drive to reduce carbon footprints, and there’s clearly an appetite to cut down on energy use.

So, what challenges do manufacturers who use biomass fermentation or precision fermentation in meat substitute production face? And how can they reduce operational expenditure, eliminate waste and optimise fermentation to maximise production?

The challenge of excessive foaming

How manufacturers tackle excessive foaming can affect both energy use and operational expenditure.

Foam is created in fermenters because of the need to agitate and aerate aerobic fermentations. However, excessive foaming can occur. If enough foam is generated, it will overflow from the gas outlet, resulting in the loss of growth media and product. In addition, foam that collects around a fermenter’s impellers can reduce agitation efficiency – and affect the fermenter’s performance.

A less visible problem is that bubbles trapped in foam will have longer residence times in fermenters. Over the duration of the residence time, the bubbles will become oxygen depleted, leading to a reduction in the Oxygen Transfer Rate: This can impact on productivity.

In addition, in some fermentations, off-gas will need to be filtered before it is released into the environment. However, if excessive foaming occurs, foam in the gas outlet can cause filter blockages. This can cause multiple problems. Blocked filters will need to be replaced, resulting in downtime. A filter blockage can also cause pressure to build up within the vessel, which can damage equipment. Plus, if the vessel is shut down because of a blockage, the fermentation process is likely to be terminated, leading to expensive production delays.

Manufacturers can use antifoam additives to control excessive foaming – but antifoam can also be a contamination source.

Direct heat exchangers or steam injection have been common methods of sterilising antifoam. However, typical antifoams have reasonably high molecular weights that result in lower solubility in water. This inhibits the effectiveness of steam as a sterilant, as it is difficult for the moist heat to achieve direct contact with the microorganism. It is also very difficult to validate that sterilisation is complete.

Sterile filtration of antifoam using Polyethersulfone (PES) membrane filters can guarantee sterility prior to the antifoam being dosed into the fermenter. Using this method means that the high energy costs associated with using direct heat exchangers or steam injection can be reduced. Validation is also easier: PES filter membrane cartridges offer validated sterility when they are handled correctly by an operator and regular integrity testing is carried out. This makes quality control more efficient.

Mechanical separation technology – which removes foam by creating a cyclone which causes foam and aerosol to migrate to an outer wall – can also be introduced. This reduces the quantity of antifoam required and so helps the manufacturer to cut down on operational expenditure. By removing foam, it can also offer additional protection to off-gas filters – again, helping the manufacturer to cut down on operational expenditure and downtime.

Tackling further contamination risks

Sterile filtration must be used to prevent contamination from the air sparged into the bottom of the fermenter to supply oxygen to the organisms (inlet air). However, fermentation generates high temperatures, which can damage filters. This damage can cause downtime while damaged filters are replaced. And if filters fail, the product could be at risk of contamination: Batches could be written off as a result. Consequently, any filters used to sterilise inlet air should be built to withstand high-temperature environments.

Microorganisms are unlikely to grow in alkali or acidic conditions – but that doesn’t mean that pH-adjusting chemicals shouldn’t be sterilised. That’s because there is a significant contamination threat from extremophiles and heat-resistant spores that can thrive in the fermenter if introduced. However, pH adjustment chemicals are corrosive to Heat Transfer Surfaces and therefore, sterile filtration of these chemicals, prior to their addition to a fermenter, is preferable.

Nutrient feeds pose a different problem. They have all the right elements to grow a healthy culture of the active microorganism, but this means that by their very nature, they provide conditions for spoilage organisms to thrive.

Direct heat exchangers and steam have often been used to sterilise nutrient feeds, however these methods require high energy use. In addition, heat transfer surfaces can suffer from corrosion, which can reduce sterilisation performance.

Sterile filtration offers an effective solution: Filters don’t generate the same maintenance issues as heat exchange methods, and are far less energy-intensive.

Finally, sterile filtration can also be used to sterilise the ‘make-up’ water that replaces water which evaporates from the fermenter. Although liquid vent losses can be replaced by steam injection, this method carries the risk of damage to the microorganism at the injection point – and also means higher energy costs.

Looking to the future

With the meat substitute market experiencing rapid growth, it’s vital that manufacturers put their fermentation processes under the spotlight – and consider technology that can drive efficiency and reduce waste.