Microbiology, Lec 17.

Announcements:

Some practice questions can now be found at: Practice Exam 2

Industrial Microbiology & Biotechnology

Besides the microbial food industry, there is also a new and thriving form of industrial microbiology which is often called the Biotechnology industry. Most biotechnological uses of microbes involve genetic manipulation to create microbes that produce products of use to humans. Big selling products include antibiotic, insulin, human growth factor, blood proteins and various vaccines.

Tables 44.5, 44.8, 44.11 and 44.13 list some of the products that are obtained from microorganisms.

WeÕve already hit upon some of the major concepts involved in the production of Microbial products:

See Lec. 14 for the relationship between microbial growth and production of primary and secondary metabolites (Figs. 44.7 - 44.9

See Lec. 16 for a discussion of continuous flow and batch type reactors (Figs. 44.2 & 44.3) used in the biotechnology industry.

Biotechnology is a booming bussiness employing thousands of microbiologists. As of 3/15/2000 the value (Market Capitalization) of just one Biotech company, i.e. Amgen Inc., = 60 billion dollars.

Environmental Microbiology.

Our goal for this part of the course is to understand the roles that microbes play in waste treatment and environmental cleanup (bioremediation). Now that we understand the physiologies of microbes and their roles in the carbon and N cycles we can apply that knowledge to environmental problems.

Why treat sewage?

1. Waterborne pathogens

2. Organic load depletes O2 in receiving water - sewage has a very high "biological oxygen demand" (BOD). (See Figure 41.16).

3. It stinks!

Because of the public health and environmental problems associated with sewage, municipalities in the U.S. are now required to treat waste water using at least a secondary wastewater treatment system.

Figure 41.17 shows a typical secondary wastewater treatment plant. Note the difference between primary and secondary treatment. Primary treatment is just a means to separate the solid from the liquid waste. Most of the microbiological action takes place in the secondary stages of treatment.

Secondary treatment. 2 main types (Figure 41.20, both mostly aerobic):

1) Trickling Filter = water is sprinkled (for aeration) over a bed of rocks (the rocks are coated with biofilms of various sorts of microbes). Analogous to a continuous flow process.

2) Activated Sludge = More of a batch process in which air is bubbled through the activated sludge unit and the microbes grow as flocs.

After one (or both) of the above treatments the fluid passes into a secondary clarifier where the residual flocs are allowed to settle out. Some of the flocs are often added back to the activated sludge tank to speed up the process (that's why its called "activated").

After the secondary clarifier the fluid is usually chlorinated and discharged into a body of water. At a minority of treatment facilities the water is further treated via tertiary treatment (see below).

Note that most of the sludge from the first and last steps ends up in the anaerobic sludge digestor. In this digestor there is a complex anaerobic food web similar to the one we discussed in lecture 8 (Table 41.5). Thus, there are a wide variety of fermentative and methanogenic microbes in anaerobic sludge digestors, and the main products are methane gas and consolidated sludge. The methane is often used as a power source for waste treatment facilities and the sludge is either put in landfills, composted or used directly as a fertilizer or soil supplement.

The main goal of tertiary treatment is to remove the inorganic nutrients released during primary and secondary treatment. These nutrients encourage algal growth (because algae are often N or P limited in nature) in natural waters and can lead to the eutrophication of water bodies (See Fig. 41.14, pg. 866).

There are many modes of tertiary treatment but we will only mention a few.....

To remove ammonia a two step process is often used. In the first step the water is aerated to encourage nitrifying bacteria (Lec. 13) who convert the NH3 to NO3-. This is followed by an anaerobic step in which the denitrifying bacteria (Lec. 13) convert (via anaerobic respiration, lecture 10) the nitrate to gaseous forms of N (e.g. N2, N2O etc.).

Constructed Wetlands (See Fig. 41.22, pg. 873)