How Spent Media Analysis Could Pave the Way to Affordable Alternative Proteins

With an ever-growing population and a climate continuing to break records for all the wrong reasons, there is more attention than ever on alternative protein sources to meet our nutritional needs while reducing our impact on the planet. Approaches have included plant-based proteins, mycoproteins, insects and cell culture. While cell culture could offer a great way to produce proteins in controlled conditions, with minimal land use and the opportunity to incorporate many of the same benefits as animal cells from the whole animal, cost has been a significant barrier to commercially viable cell cultured food products.

We spoke to Professor Jenny Nelson, UC Davis and Agilent Technologies, and Edward O’Neill, UC Davis, to find out how spent media analysis could help to drive down costs and make cell cultured proteins an affordable reality for consumers.

Q: For those who may be unfamiliar with the concept, what can spent media analysis tell us, how do you analyze it and what do you look for?

A: To grow in culture, animal cells require highly complex media, composed of various nutrients such as glucose, amino acids, vitamins and minerals. Different cell types have different metabolic needs, and different culture conditions can affect a cell type’s metabolic behavior. So, if we want to optimize our cell culture media as much as possible to achieve the lowest cost for a given application, we need to know exactly how much of the various media nutrients our cells will require during their growth period. Spent media analysis is a way to gain this kind of understanding of what your cells actually need to grow and be healthy in culture. To do this, we grow our cells in culture and take samples of the media at various points over time. We can then analyze the samples using standard analytical techniques like high performance liquid chromatography (HPLC) and inductively coupled plasma-mass spectrometry (ICP-MS). HPLC methods are typically used to check levels of nutrient compounds in the spent media samples while ICP-MS methods can determine a large number of major and trace elements, including heavy metals.

Q: How does spent media analysis help us to optimize the development of alternative protein sources?

A: Unlike existing cell culture biomanufacturing applications, alternative protein foods like cultivated meat have enormous pressure to be very low cost and competitive with conventional protein foods. Until now, there have not been efforts to reduce costs of industrial animal cell culture since most previous applications (like pharmaceuticals) involve very high value final products. As culture media is the leading cost driver of many alternative protein foods, there is a great need to find ways to optimize and reduce the costs of the media. Spent media analysis is a tool that can help us lower the costs of cultivated meat by making the media as efficient as possible for a given cell type, while also ensuring its safety through monitoring elements such as arsenic, cadmium, mercury and lead.

Q: Were there any surprising findings that have come out of these studies?

A: The most surprising finding from our data was that the majority of spent media analytes we looked at did not appear to be changing significantly in concentration over time during cell culture. For instance, none of the water-soluble vitamins or minerals that we measured by HPLC and ICP-MS, respectively, seemed to decrease in concentration over time. Many amino acids also did not appear to be depleted. This would suggest that we could potentially reduce or completely remove those media components to help significantly reduce costs.

Figure 1: Analysis of mineral concentrations in spent media from cultures of three cultivated meat-relevant cell types. Credit: Image recreated under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Taken from O’Neill EN et al. 2022,¹ the order and scales have been altered to improve the clarity of the data.

Q: What are the biggest challenges in implementing changes from the information gathered by these analyses?

A: We don’t know yet how the presence or absence of many media components influences cell growth and viability. We can’t necessarily assume that cells will behave the same if we adjust the concentrations of media components according to our spent media analysis results. It could be that certain components are metabolically cycled by the cells, resulting in no detectable change in concentration in the media, but still being necessary at certain concentrations for cell growth. More extensive cell culture studies using adjusted media formulations will likely need to be performed to address these questions.

Q: Do you think that the work needed to optimize cell culture media to individual cell lines and species could be a barrier to using cell culture as an affordable alternative protein source?

A: This could be a barrier in the near term to the easy development of a wide variety of alternative protein products and production schemes. However, it presents a great opportunity for new innovation in analysis techniques and solutions to make the process simpler and less expensive. Otherwise, there is the possibility that novel media formulations based on significantly less expensive ingredients (such as plant hydrolysates, which we are currently testing at UC Davis) can be developed, such that the overall costs will be low enough for most cell types to not require tailored optimization via spent media analysis.

Reference: 1. O’Neill EN, Ansel JC, Kwong, GA et al. Spent media analysis suggests cultivated meat media will require species and cell type optimization. npj Sci Food 6, 46 (2022). doi:10.1038/s41538-022-00157-z

Professor Jenny Nelson and Edward O’Neill were speaking to Dr. Karen Steward, Senior Science Writer for Technology Networks.

About the interviewees

Jenny Nelson

Jenny received her PhD in analytical chemistry from the University of Cincinnati in 2007, and her MBA from Saint Mary’s College of California in 2011. Currently, Jenny is an application scientist at Agilent Technologies, joining in 2012. Jenny is also an adjunct professor in the Department of Viticulture and Enology at the University of California, Davis, a position she has had since 2013. Jenny has been very active with the Association of Official Agricultural Chemists (AOAC) and the American Society for Testing and Materials (ASTM) over the past eight years, serving on expert review panels, chairing committees and volunteering to develop new methods needed by the industry. Jenny has extensive experience in operating and method development for ICP-MS, inductively coupled plasma-optical emission spectroscopy (ICP-OES), and microwave plasma-atomic emission spectroscopy (MP-AES).

Edward O’Neill

Ted is a fifth year PhD candidate in Food Science and Technology at UC Davis. Having followed a plant-based diet for 15 years, he is passionate about the expanding alternative protein space and innovative food technologies. Supported by a New Harvest Fellowship, he was one of the first two graduate students at UC Davis to begin researching cultivated meat in 2019 and has helped grow the UC Davis Cultivated Meat Consortium to more than 50 researchers today. Specifically, his research aims to identify ways to reduce costs of cell culture media by employing spent media analysis and substituting plant extracts and hydrolysates for purified amino acids and growth factors. In 2020, he co-founded the Davis Alt Protein Project, a student organization promoting interest and engagement with the alternative protein field. He holds BS degrees in Molecular and Cell Biology, and Physiology and Neurobiology from the University of Connecticut.