Center for Algal Innovations: RCM Project

The Problem

Aquaculture is among the fastest growing food production sectors in the world and this is due in part to increasing concerns surrounding food insecurity. Even though this has led to the culturing of a wide variety of aquatic organisms, production has predominantly been focused on finfish and shellfish species. For instance, the farming of oysters (Figure 1.) has taken place for a very long time and today the industry is primarily a combination of land-based hatcheries and bottom/off-bottom grow out sites. In recent years shellfish growers have experienced a lot of production woes, including increased disease pressure and issues of uncertain water quality. If shellfish aquaculture continues to be negatively impacted by these and other environmental stressors then the industry will need to develop new economic or technological approaches to successfully address gaps in production.

The Challenge

Many shellfish growers are developing new culturing methods to combat the uncertainty surrounding poor water quality as it continues to hamper the industry. Innovations have included a shift away from facilities reliant on continuously flowing filtered seawater to newer systems capable of cleaning and recirculating water with minimal input. Moreover, they are looking to offset the cost of these new systems through lowering production costs elsewhere. For example, a considerable cost of doing business for many shellfish farmers involves the production of microalgae (Figure 2.). Microalgae are used specifically for the shellfish’s diet and are often cultured onsite in large volumes requiring additional resources and labor. Microalgae are aquatic microscopic unicellular organisms capable of carrying out photosynthesis, converting sunlight, water, and inorganic compounds into biomass. Typically, several well-known species of microalgae are intensively cultured before being fed to the shellfish being reared. Inorganic compounds, vitamins, and minerals are routinely added to water in order to create an enriched culturing media for the microalgae. The addition of nutrients for algal culture represents a considerable expense in the overall production of a farmed shellfish. For this reason, shellfish aquaculture could benefit economically from identifying new, cost-effective, sources of nutrients which could be utilized in microalgae culture to supplement or replace a range of higher priced nutrients currently incorporated into many microalgae media recipes.

The Solution

The Center for Algal Innovations (CAI) has partnered with a local oyster grower to investigate the utilization of spent brewer’s yeast as a potential revalorized culture media (RCM) feedstock. Spent brewer’s yeast is an underutilized waste stream product generated by the brewing industry and is a readily available, cost-effective, byproduct of beer production. If the nutrient profile (protein, carbohydrate, inorganic compounds) of the brewer’s yeast can be made bioavailable via autolysis, a process where heat and time break down cells into their components (Figure 3.), then there may be an opportunity to shift microalgae media recipes away from higher priced inorganic nutrient salts to cost-effective nutrients found in revalorized products. Specifically, exploiting the discarded yeast produced by beer industry could be a valuable way to produce an alternative low-cost culture media capable of supporting microalgae production.

Current Progress on the RCM Project

The RCM project is currently in its early stages. Nutrient profiles for the autolyzed RCM are being established at this time and will be used to help formulate prospective media recipes to culture microalgae. Furthermore, a number of potential species of microalgae, commonly used in shellfish aquaculture, have been selected and will soon undergo growth trials to evaluate the viability of the spent brewer yeast RCM.