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Although more experiments and probably needed, agitation is believed to be an important factor for any species of microbe (yeast and bacteria). Gentle stirring on a stir plate or orbital shaker, or frequent gentle manual agitation leads to faster growth and a higher number of organisms. Agitation keeps the microbes in solution. It also maximizes the microbes' access to nutrients and disperses waste evenly. In a non-agitated starter, the microbes are limited to the diffusion rate of nutrients, leading to a slower and more stressful growth <ref name="BryanHeit_starters">[https://www.facebook.com/groups/MilkTheFunk/permalink/1168024059892473/?comment_id=1174865305875015&reply_comment_id=1176092372418975&total_comments=1&comment_tracking=%7B%22tn%22%3A%22R9%22%7D Conversation with Bryan of Sui Generis Blog about starters and agitation. 11/09/2015.]</ref>. For more information regarding aeration and agitation effects on ''Brettanomyces'' growth, see [[Brettanomyces_Propagation_Experiment|Mark Trent's Brettanomyces Propagation Experiment]].
The starter should be stored at room temperature for 5-7 days, or can be stored at a higher temperature if bacteria is the main microbe that the brewer is after. Monitor the starter for activity during this time to ensure that there are viable microbes. Visual activity may not always be present, may be brief, or minimal. Monitoring the pH and the gravity can assist the brewer with deciding whether or not the commercial sour beer has any viable microorganisms still alive in it. If the starter krausens within 2-3 days then it might have viable ''Saccharomyces'', otherwise strains of ''Saccharomyces'' might be dead (especially if the beer was not freshly bottled and was a low pH sour beer). ''Brettanomyces'' may not show signs of fermentation for up to 3-7 days. After 7 days, create a another 1 liter starter of DME wort, and add the original 200 mL dregs starter to it. Repeat the process above, giving the 1 liter starter another 5-7 days of growth <ref name="preiss"></ref>. Pitch the 1 liter starter into a ~20 liter batch of wort, or continue to step up the starter for larger batch sizes.
===Supplementing another fermentation===