138 ◾ Fundamental Food Microbiology
5. What are the different types of food carbohydrates transported inside the lactic acid bacterial cells? Explain the functions of β-galactosidase and phospho-β-galactosidase.
6. Define homolactic and heterolactic fermentation of carbohydrates by lactic acid bacteria.
Give three examples of lactic acid bacteria in each fermentation group.
7. List the end products (including energy generation) of homolactic and heterolactic fermentation when glucose is used as a substrate. Which enzymes play crucial roles in each pathway?
8. How are galactose, galactose-6-phosphate, and fructose metabolized by the EMP pathway
by homolactic fermentors? List three species from three genera that produce only l(+)-lactic
acid from glucose.
9. Why is the bifidus pathway of the metabolism of hexose also called the fructose-phosphate
shunt? What are the end products?
10. How is citrate transported and metabolized to produce diacetyl by some lactic acid bacteria?
List two species from two genera that produce diacetyl from citrate. How can other lactic
acid bacteria produce diacetyl from carbohydrate metabolism?
11. Pyruvate can be used to produce products other than lactic acid. List four such products and
show the reactions involved in their production.
12. Briefly discuss how food proteins and food lipids are transported and metabolized by starterculture bacteria.
References
1. Fox, P.F., Bacteria, beneficial—Lactic acid bacteria: An overview. In Encyclopedia of Dairy Sciences
(Second Edition), John, W.F., Ed., Academic Press, San Diego, 2011, pp. 401–402.
2. Mayo, B., Aleksandrzak-Piekarczyk, T., Fernández, M., Kowalczyk, M., Álvarez-Martín, P., and
Bardowski, J., Updates in the metabolism of lactic acid bacteria. In Biotechnology of Lactic Acid Bacteria,
Mozzi, F., Raya, R.R., and Vignolo, G.M., Eds., Wiley-Blackwell, 2010, pp. 3–33.
3. Pedersen, M.B., Gaudu, P., Lechardeur, D., Petit, M.-A., and Gruss, A., Aerobic respiration metabolism
in lactic acid bacteria and uses in biotechnology, Annu. Rev. Food Sci. Technol., 3, 37–58, 2012.
4. Kandler, O., Carbohydrate metabolism in lactic acid bacteria, Antonie Van Leeuwenhoek J. Microbiol.,
49, 209–224, 1983.
5. Thompson, J., Lactic acid bacteria: Novel system for in vivo studies of sugar transport and metabolism
of Gram-positive organisms, Biochimie, 70, 325–336, 1988.
6. Vos, W., Metabolic engineering of sugar catabolism in lactic acid bacteria, Antonie van Leeuwenhoek, 70,
223–242, 1996.
7. Thomas, T.D. and Pritchard, G.G., Proteolytic enzymes of dairy starter cultures, FEMS Microbiol. Rev.,
46, 245–268, 1987.
5. What are the different types of food carbohydrates transported inside the lactic acid bacterial cells? Explain the functions of β-galactosidase and phospho-β-galactosidase.
6. Define homolactic and heterolactic fermentation of carbohydrates by lactic acid bacteria.
Give three examples of lactic acid bacteria in each fermentation group.
7. List the end products (including energy generation) of homolactic and heterolactic fermentation when glucose is used as a substrate. Which enzymes play crucial roles in each pathway?
8. How are galactose, galactose-6-phosphate, and fructose metabolized by the EMP pathway
by homolactic fermentors? List three species from three genera that produce only l(+)-lactic
acid from glucose.
9. Why is the bifidus pathway of the metabolism of hexose also called the fructose-phosphate
shunt? What are the end products?
10. How is citrate transported and metabolized to produce diacetyl by some lactic acid bacteria?
List two species from two genera that produce diacetyl from citrate. How can other lactic
acid bacteria produce diacetyl from carbohydrate metabolism?
11. Pyruvate can be used to produce products other than lactic acid. List four such products and
show the reactions involved in their production.
12. Briefly discuss how food proteins and food lipids are transported and metabolized by starterculture bacteria.
References
1. Fox, P.F., Bacteria, beneficial—Lactic acid bacteria: An overview. In Encyclopedia of Dairy Sciences
(Second Edition), John, W.F., Ed., Academic Press, San Diego, 2011, pp. 401–402.
2. Mayo, B., Aleksandrzak-Piekarczyk, T., Fernández, M., Kowalczyk, M., Álvarez-Martín, P., and
Bardowski, J., Updates in the metabolism of lactic acid bacteria. In Biotechnology of Lactic Acid Bacteria,
Mozzi, F., Raya, R.R., and Vignolo, G.M., Eds., Wiley-Blackwell, 2010, pp. 3–33.
3. Pedersen, M.B., Gaudu, P., Lechardeur, D., Petit, M.-A., and Gruss, A., Aerobic respiration metabolism
in lactic acid bacteria and uses in biotechnology, Annu. Rev. Food Sci. Technol., 3, 37–58, 2012.
4. Kandler, O., Carbohydrate metabolism in lactic acid bacteria, Antonie Van Leeuwenhoek J. Microbiol.,
49, 209–224, 1983.
5. Thompson, J., Lactic acid bacteria: Novel system for in vivo studies of sugar transport and metabolism
of Gram-positive organisms, Biochimie, 70, 325–336, 1988.
6. Vos, W., Metabolic engineering of sugar catabolism in lactic acid bacteria, Antonie van Leeuwenhoek, 70,
223–242, 1996.
7. Thomas, T.D. and Pritchard, G.G., Proteolytic enzymes of dairy starter cultures, FEMS Microbiol. Rev.,
46, 245–268, 1987.