Lecture 12: Single cell protein Flashcards
What is single cell protein (SCP)?
production of protein from biomass of different microbial sources. E.g., bacteria, yeasts, moulds, and micro-algae
What are the advantages of SCP over animal protein?
- Rapid growth rate and high productivity
- High protein contant, 30-80% dry weight
- Ability to use a range of substances
- Strain selection and further development
- Occupies little land area
- Production indpendent of season
- Consistent quality
What makes a suitable SCP microbe?
- Growth rate
- Temperature and pH tolerance
- Oxygen requirements
- Growth morphology
- Genetic stability
- Ease of recovery of product
- Structure and composition of final product
What are the safety considerations of SCP
- One concern: elevated nucleic acid levels (especially RNA)
- Digestion of RNA keads to generation of purine compounds, leading to excess uric acid, which can crystallise in joint to give gout-like symptoms or kidney stones
What are the costs and carbon levels in SCP
Cost is dependent on many variables, but major cost is the carbon substrate (50-60%).
Renewable sources like agriculture, diary, wood are desirable
What should be considered when choosing a substrate
- Cost
- Availbaility
- Biomass yield
- Oxygen requiement
- Heat produced during fermentation
- Downstream processing costs (eg toxic compound removal)
What are the general, basic stages common to SCP processes
- medium preparation (substarate pre-treatment)
- Fermentation
- Separation and downstream processing
What is the Bel Process
Dairy industry generates 80 million tonnes of whey per year, containing 45g/l lactose and 10g/l protein
Whey is a potential pollutant with COD-60g oxygen / litre
Good for the production of SCP from lactose utilising yeasts
Whey pasteurised, lactose concentration reduced, mineral salts added, fermented at 38C, pH 3.5. Yeasts utilise lactose and attain a biomass 25g/L
What is the Symba process
Developed in sweeden for SCP for animal feeds and potato waste
Potato waste high in starch (not good for many organisms), which is used by two mciroorganisms:
Saccharomycopsis fibuligera
Candida utilis
What is the Pruteen Process?
- Uses methanol, completely miscible with water, and as its availble in very pure form, protein produced doesnt need purification
- However, only low concentrations are tolerated by microbes
- Attempts to develop methanol-based process was made by US, EU, Japan, USSR
- Production stopped in 1987 due to rise in methanol cost
- was used to make feed for chickens, pigs, veal calves
What is Quorn?
1991, Marlow foods build a production plant to grow a species of Fusarium graminearum isolated from soil in Buckinghamshire, now called QUORN
12% protein, no animal fat or cholesterol, appearing to help reduce fats in blood stream
1000 tonnes produced each year in the 40m^3 airlift fermenter. Operated continuously at 30C pH6
Ammonia used to control pH and act as nitroge source
Oxygen supplied as sterile compressed air and tightly regulated. Too low oxygen = anaerobic metabolism, gives by-products of the quorn. Too high = loss of productivity.
How is quorns fibrous natuer made>
Hyphae with an average length of 0.4mm and cross sectional diameter of 10um
IF grown in prolonged culture, highly branched forms of fungus can occur after approx 100-1200 hours, losing the fibrous nature
What is the final biomass of Quorn
10% RNA - far too high for human consumption
Reduced by thermal shock of 64C for 30 minutes, rendering fungus not viable and activates RNAses to break down RNA into nucleotides which diffuse out the cell
RESULT = 2% RNA
What is the substrate for Quorn?
Glucose (much cheaper than petroleum)
What is Dihe?
Cyanobacterium “Spirulina platensis” used to make Dihe in Africa.
Taken from lake Chad, poured into hole, dried and cut into chunks to be sold. VERY HEALTHY
