Originally Posted by Jack
Why only dextrose?
Well, at least not a malt-based sugar (DME, saved wort, etc.). Lager yeasts can produce fruity off-flavors during fermentation (or carbonation) if done at too warm temps (compared to the optimum range for primary fermentation). So, say you wanted to brew a lager per the Reinheitsgebot. You could use saved wort for carbonation, but you'd have to carb at primary fermentation temps to avoid potential fruitiness, e.g., 50dF. Lager yeasts ferment dextrose clean at room temp. So, it's OK to carb lagers at room temp if you're using dextrose.