145
their effects on the gastrointestinal tract and the risk of allergies. The carcinogenic
and toxicological potentials should also be evaluated so, feeding trials are also
needed. The process of harvesting, drying and processing can also affect the nutritional values of the microbial protein. Microbial protein composition depends on
the type of substrate and organism used. Proteins not only provide nutritional value
but they are also involved in a number of other functions (Upadhyaya et al. 2016).
Microbial protein from yeast and fungi has 50–55% protein. It has high protein
and carbohydrates ratio. It contains large number of lysine residues and less number
of methionine and cysteine residues. It also provides good balance of amino acids
and it contains high B complex vitamins. Few yeast strains have probiotic characteristics like Saccharomyces cerisiae and Debaryomyces hansenii. Microbial proteins produced by utilizing bacteria comprise more than 80% protein even though
they contain a small amount of sulphur containing amino acids with high nucleic
acid content (Upadhyaya et al. 2016).
Excellent nutrient profiles and the possibility of economical mass production
make microbial proteins a potential solution for the ongoing food crisis. They are
also used in aquaculture feeding as a replacement for fishmeal and for protection of
rotifer and Artemia. Yeast proteins have revolutionized the aquaculture diets. Few
yeast strains with probiotic characteristics, like Debaryomyces hansenii and
Saccharomyces cerevisiae have the ability to boost survival of larvae either by residing in the fish gut, thus eliciting the early maturation of the pancreas, or through the
immune exciting glucans derived from the yeast cell walls. The idea that microbial
proteins can be the solution of food shortages in the less developed countries is
gaining research interests among scientists. To assure future success of microbial
proteins, first, food technology problems need to be resolved in order to make it
comparable to the conventional foods and second, the production should equate
favorably with other protein sources (Suman et al. 2015).
8.6 Harmful Effects of Microbial Proteins
The potentials that microbial proteins can do to human beings and the world’s problem on hunger are gaining special interests but concerns regarding their acceptability, safety and potential toxicity are emerging. For one, high nucleic acid content in
microbial proteins can be a problem which is noted to be beyond the acceptable
level of 71%. To address this, nucleic acid can be removed or reduced with either
one or all of the following methods: by the chemical treatment with sodium hydroxide, treating the cells with 10% sodium chloride, activating endogenous nucleases
in last step of biomass production and thermal shock. Hueihsiung Yang developed a
modest technique to reduce the nucleic acid content in Brevibacterium NNJM98A
by incubating non-proliferating cells at a pH of 10.3 and 55 °C for 3 h (Upadhyaya
et al. 2016).
Another issue is the presence of cell walls that cannot be digested. As with yeast
and algae, there might be intolerable colour and flavours, and live cells of organisms
8 Microbial Proteins: A Potential Source of Protein
their effects on the gastrointestinal tract and the risk of allergies. The carcinogenic
and toxicological potentials should also be evaluated so, feeding trials are also
needed. The process of harvesting, drying and processing can also affect the nutritional values of the microbial protein. Microbial protein composition depends on
the type of substrate and organism used. Proteins not only provide nutritional value
but they are also involved in a number of other functions (Upadhyaya et al. 2016).
Microbial protein from yeast and fungi has 50–55% protein. It has high protein
and carbohydrates ratio. It contains large number of lysine residues and less number
of methionine and cysteine residues. It also provides good balance of amino acids
and it contains high B complex vitamins. Few yeast strains have probiotic characteristics like Saccharomyces cerisiae and Debaryomyces hansenii. Microbial proteins produced by utilizing bacteria comprise more than 80% protein even though
they contain a small amount of sulphur containing amino acids with high nucleic
acid content (Upadhyaya et al. 2016).
Excellent nutrient profiles and the possibility of economical mass production
make microbial proteins a potential solution for the ongoing food crisis. They are
also used in aquaculture feeding as a replacement for fishmeal and for protection of
rotifer and Artemia. Yeast proteins have revolutionized the aquaculture diets. Few
yeast strains with probiotic characteristics, like Debaryomyces hansenii and
Saccharomyces cerevisiae have the ability to boost survival of larvae either by residing in the fish gut, thus eliciting the early maturation of the pancreas, or through the
immune exciting glucans derived from the yeast cell walls. The idea that microbial
proteins can be the solution of food shortages in the less developed countries is
gaining research interests among scientists. To assure future success of microbial
proteins, first, food technology problems need to be resolved in order to make it
comparable to the conventional foods and second, the production should equate
favorably with other protein sources (Suman et al. 2015).
8.6 Harmful Effects of Microbial Proteins
The potentials that microbial proteins can do to human beings and the world’s problem on hunger are gaining special interests but concerns regarding their acceptability, safety and potential toxicity are emerging. For one, high nucleic acid content in
microbial proteins can be a problem which is noted to be beyond the acceptable
level of 71%. To address this, nucleic acid can be removed or reduced with either
one or all of the following methods: by the chemical treatment with sodium hydroxide, treating the cells with 10% sodium chloride, activating endogenous nucleases
in last step of biomass production and thermal shock. Hueihsiung Yang developed a
modest technique to reduce the nucleic acid content in Brevibacterium NNJM98A
by incubating non-proliferating cells at a pH of 10.3 and 55 °C for 3 h (Upadhyaya
et al. 2016).
Another issue is the presence of cell walls that cannot be digested. As with yeast
and algae, there might be intolerable colour and flavours, and live cells of organisms
8 Microbial Proteins: A Potential Source of Protein