There is a strong consensus in yeast micro that DME (not sucrose, dextrose etc) should be used to make a starter.
DME provides a source of nutrients and amino acids which are esstential for yeast growth, whereas sugar does not.
Some other food for thought I found after a bit of reading.
http://www.microbrewers.net/2009/make-a-yeast-starter/
"The reason to use DME over other fermentables is to get the yeast acclimated to the environment they are going to be in and to build strong and healthy cell walls and membranes. You wouldnt put your freshwater fish in a saltwater tank so dont put your yeast in an unhealthy environment."
Palmer
http://www.howtobrew.com/section1/chapter6-6.html
"The starter wort and the main wort must be very similar if the starter is pitched at or near peak activity. Why? Because the yeast in the starter wort have produced a specific set of enzymes for that wort's sugar profile. If those yeast are then pitched to a different wort, with a different relative percentage of sugars, the yeast will be impaired and the fermentation may be affected. Kind of like trying to change boats in mid-stream. This is especially true for starter worts made from extract that includes refined sugars. Yeast that has been eating sucrose, glucose/dextrose, or fructose will quit making the enzyme that allows it to eat maltose - the main sugar of brewer's wort."
http://www.mrmalty.com/starter_faq.htm
"Use an all malt wort for starters. The sugar in the starter needs to be maltose, not simple sugar. Yeast that have been eating a lot of simple sugars stop making the enzyme that enable it to break down maltose, which is the main sugar in wort. The yeast quickly learn to be lazy and the ability to fully attenuate a batch of beer suffers."
http://www.maltosefalcons.com/tech/yeast-p...s-and-practices
The addition of yeast nutrients and certain salts can also improve yeast growth and are a worthwhile addition to starters. Yeast nutrients usually are of two types, one which is ammonium phosphate-based, and the other which is amino acid/peptide and vitamin-based (similar to the peptone and yeast extract in the laboratory media described below). Both serve the same basic function which is to increase the nitrogen content of the wort and yeast. A mixture of different nitrogen sources have been shown to enhance both growth and fermentation and suggest that the amino acid/peptide-based nutrients may be more appropriate than diammonium phosphate. Also rapidly growing yeast such as those in starters have a higher than normal nitrogen requirement. Thus starter worts should be supplemented with yeast nutrients so that nitrogen is not limiting.
Table 3. Recommended Media for Starter
Starter Wort Amount for 1 Liter (qt)
Dry Malt Extract or
~1.040 O.G. wort 1 cup or 0.25 lbs DME
1% vitamin based yeast nutrient 1/2 tsp or 10 g
Hops (optional) 1 pellet or a few drops of iso-alpha extract
http://www.whitelabs.com/beer/homebrew_FAQ.html - Cascade brewery have similar instructions
"Procedure:
In a medium sauce pan, add 2 pints of water and 1 cup Dried Malt Extract (DME). Mix well and boil the solution for about 10 minutes to sterilize. Cover and cool the pan to room temperature in an ice bath. This will give you a wort of approximately 1.040 OG. Keeping the Original Gravity low is important because you want to keep the yeast in its growth phase, rather than its fermentation phase. The fermentation phase will create alcohol which can be toxic to yeast in high concentrations"
http://www.picobrewery.com/askarchive/starter.htm
"Yeast undergoes a series of metabolic steps when it is pitched into wort. It takes a while for the yeast to figure out what to do. When yeast is poured from the tube or package directly into wort, they are in a dormant state. They don't immediately begin fermentation. The first thing they do is to assess the level of nutrients, including sugar, amino acids and oxygen levels. Once they've adapted to the environment, they begin a reproductive phase. They will continue to reproduce as long as oxygen and other nutrients are available. Fermentation begins in earnest only once all the oxygen has been depleted."
It seems the problem of overpitching is minimal
http://www.homebrewtalk.com/wiki/index.php/Overpitching
Overpitching is when too much yeast is pitched into the wort. If this occurs, the most common symptoms is a very yeasty-flavoured beer, beer that is fermented too quickly and has high fermentation temperatures as a result. This is a very uncommon in a home brewing setup for the following reasons:
1- Most yeast packets- even liquid yeast starters- are considered by experts in the field to be either *just* enough yeast to ferment a 5 gallon batch or even to be underpitching.
2- It takes a lot of yeast to overpitch.
If you want to be anal you can use a yeast pitching calc like this one:
http://www.mrmalty.com/calc/calc.html
cheers,
piraterum