Fundamental Food Microbiology, Third Edition - Fuad Fathir

CONTENTS
137
CHAPTER 11
Biochemistry of Some Beneficial Traits
I. Introduction ..............................................................................................137
II. Mechanisms of Transport of Nutrients ....................................................138
III. Transport and Metabolism of Carbohydrates ..........................................139
A. PEP-PTS System for Lactose Transport in Lactococcus lactis ......139
B. Permease System for Lactose in Lactobacillus acidophilus............140
C. Carbohydrates Available inside the Cells for Metabolism ..............140
D. Homolactic Fermentation of Carbohydrates ...................................140
E. Heterolactic Fermentation of Carbohydrates ...................................143
F. Metabolism of Pentoses ...................................................................143
G. Hexose Fermentation by Bifidobacterium .......................................145
H. Diacetyl Production from Citrate ....................................................145
I. Propionic Acid Production by Propionibacterium ..........................145
IV. Transport and Metabolism of Proteinaceous Compounds
and Amino Acids ......................................................................................145
V. Transport and Metabolism of Lipid Compounds......................................148
VI. Conclusion ................................................................................................148
References ............................................................................................................149
Questions ..............................................................................................................149
I. INTRODUCTION
The beneficial microorganisms metabolize some of the components present in the
starting materials (i.e., food, such as milk or meat) to produce energy and cellular
materials and to multiply. In the process, they produce some end products that are
no longer necessary for the cells, and therefore these by-products are excreted in
the environment. Some of these by-products impart unique characteristics (mostly
texture and flavor) to the remaining components of the starting materials. These are