This article includes the lecture entitled “Production of protein intended for animal feed from microorganisms”, given by Professor Dr. Mª de Àngels Calvo Torras, of the Faculty of Veterinary, of the Autonomous University of Barcelona (UAB) in the end of academic year ceremony of 2017.

Currently, one of the biggest problems facing the world is the rate of population growthand consequently it is very difficult for conventional agriculture to provide enough food for such a huge number of populations. For this reason, the research of protein sources has motivated the development of new agricultural techniques, to obtain cereals with high protein content, and even the extraction of proteins from liquid units  through ultrafiltration.

Another important line of research is based on the production and obtaining of high protein content, which can contribute to microbial biomass. The ability of microorganisms to grow on various substrates helps produce this microbial biomass, known as unicellular protein, with the development of microorganisms such as bacteria, yeast, algae and fungi, for the production of animal feed and for humans. The name of this technique refers to the unicellular or filamentous state of the microorganisms used for its production, unlike the proteins obtained from pluricellular living beings, such as plants and animals.

For a long time, man had already recognized the nutritional value of certain microorganisms, such as yeasts and certain filamentous fungi.

Although the ingestion of proteins from microorganisms is not accepted by certain consumers due to its flavor, we must not forget that it is a great source of protein: while from 1,000Kg of soy, 10Kg of protein is produced daily, the protein production of 1,000Kg of bacteria reaches up to 100,000 million kilos. This is mainly due to the time required to double the mass of the microorganisms. Consequently, we can say that bacteria and yeast double their mass in a period of 20 to 120 minutes, unlike growing plants that take between 1 to 2 weeks and, for example, a pig that achieves between 4 and 6 weeks.

ADVANTAGES
The production of proteins by microorganisms has many advantages, which we can summarize, considering that:
• In optimal conditions, their growth rate is very fast, but they are sensitive to changes in pH.
• The genetic modification of microorganisms, where appropriate, is easier than in the case of plants and animals.
• Proteins obtained from microorganisms have a high nutritional value.
• Microorganisms can be grown in bulk, that is, in large quantities in relatively small containers.
• Microorganisms are able to feed on a wide range of reject products, and some are able to degrade even cellulose from plants.

A fundamental aspect is the selection and control of microorganisms, since they do not have to be pathogenic or produce or accumulate toxic compounds.
Among the genera of bacteria, most used for protein production we can name: Methylomonas, Pseudomonas, Bacillus and Aerobacter, by the fact that they are able to double in a period of 20 to 30 min and to have a high content of proteins that can reach 85%. Among the yeasts we will mention: Candida utilis, Saccharomyces cerevisiae and Kluyveromyces fragilis, used in both human and animal feed. In relation to mycelial fungi we will mention that they grow more slowly than bacteria and yeasts and among the species of choice we can mention: Paecilomyces variotii, Gliocladium deliquescens and Fusarium graminearum.

The microorganisms used in the production of biomass have to be inoculated in favorable medium (sterilized) and under nutritional conditions, which include:
– Homogenize the thin material, so that it is easy for the microorganism to metabolize it or eliminate microbial growth inhibiting agents.
– Enrich the medium with nutrients such as nitrogenous salts and phosphorus, to serve as a mineral source.
– Adjust the pH and humidity of the substrate to favor the growth of microorganisms involved.
– Apply heat treatments to eliminate pathogenic microorganisms from the matrix or raw material.

DISADVANTAGES
• Sometimes, the protein obtained does not have the characteristics of smell, texture and color.
• It can produce a slow or no digestion in the digestive tract of humans and animals, especially in terms of algae and this can cause indigestion and / or allergic reactions.
Other products of interest for feed obtained from microorganisms are: carbohydrates, fats, vitamins and minerals, as well as food additives of the type of amino acids.

RESEARCH PROJECT

Fermentation of agricultural by-products and slaughterhouse waste to replace soybeans

Research team
The team is made up of members of the research groups of the Autonomous University of Barcelona (UAB, for its initials in Catalan):

• Applied and Environmental Microbiology Group of the Animal Anatomy Department. Prof. Responsible Dr. M. Àngels Calvo.
• Ruminant Research Group of the Department of Animal and Food Science. Prof. Responsible Dr. Gerardo Ceja.
• Organic Solid Waste Composting Group of the Chemical Engineering Department. Prof. Responsible Dr. M. Teresa Gea.

REPORT
Background
The treatment of industrial waste poses an important environmental problem due to its volume, and its physical-chemical characteristics. In recent years, a large number of research projects and publications have been carried out, which propose adding value to different types of by-products (Balandran-Quintana et al., 2015, Jahurul et al., 2015, Palumbo et. al., 2015). It must be borne in mind that many of the industrial waste and by-products contain carbohydrates (sugars and fiber) and / or proteins, which can be used as substrates, either directly or after biological transformations, to obtain high-value compounds for animal feeding (Bellaver et al., 2005, Molina-Alcaide et al., 2008, Molina-Alcaide and Yánez-Ruiz, 2008, Soto et al., 2015).

From the study carried out the previous year, different types of more suitable by-products could be selected to carry out the research that is being considered and preliminary studies have also been done for the selection of groups of microorganisms of interest in achieving the desired transformations.

The final composition of the products obtained depends on the type of substrate and inocula used, as well as to the conditions of the fermentation process, which has been the subject of very few studies in the case of agricultural and agri-food waste.

From the first studies carried out we propose to work on fruit residues, dairy industry residues, molasses and also on contaminated algae of river channels and that make it difficult to manage the water of these rivers properly and their subsequent elimination when they are removed of the course of the waters.

OBJECTIVES
The main objectives of the project are:

• To study the fermentative characteristics and optimization factors of the fermentation process, including innovative microbial inoculants, for their profitability and the quality of the obtained products.
• To study the composition and nutritional assessment of the products obtained for use as protein supplements for animal feed.

RESEARCH PLAN

Activity 1

Fermentation study of the selected materials

In a first phase the fermentation potential of the selected substrates will be determined, on a laboratory scale and at a controlled temperature, in test tubes to make a first selection, and later those that allow obtaining better results will be developed on the selected substrates at different scales: 500 ml flask and finally 1 L reactors equipped with pressure measurement for the calculation of the biogas produced (Ponsà et al., 2011).

Innovative inoculants will use lactic bacteria, yeasts and a mixture consisting of milk bacteria, yeasts and phototrophic bacteria. The improvement of the digestibility of the waste and its nutritional power and, in parallel, the production of biogas, a source of renewable energy, will be evaluated.

The results obtained with the different microorganisms will be compared when developing on substrates, such as:
– Residue of fruits: apples and oranges
– Algae coming from the channels of the Ebro river and that represent a serious source of waste, when they want to eliminate
– Molasses
– Dairy products residues
– Slaughterhouse waste

Microbial strains isolated from different substrates will be used (Ávila et al., 2014). From the fermentation potential and the characteristics of the waste, the selection of the materials will be carried out, including the formulation of possible mixtures.

In the formulation, the quantity and seasonality with which these residues are generated will also will be factor in. Once the optimal substrates have been defined, the fermentation of the best potential substrates in higher volume bioreactors will be evaluated (Maulini-Duran et al., 2015).

The final samples obtained will be kept for analysis to Activity 2.

Activity 2

Study of the composition and nutritional assessment of the products obtained for use as protein supplements in animal feed

The evaluation of the nutritional value of the samples obtained from the previous activity is proposed. The chemical composition of the samples will be determined following the classic schemes of Weende and Van Soest (AOAC, 2003).

NOTE

* This article has been published in the journal of the Academy of Veterinary Sciences of Catalonia (ACVC, for its initials in Catalan) of the year 2017.