Lactococcus lactis is a Gram-positive bacteria used extensively in the production of buttermilk and cheese. L. lactis are cocci that group in pairs and short chains, and depending on growth conditions appears ovoid with typically 0.5 - 1.5 �m in length. L. lactis do not produce spores (non-sporulating) and are not motile (non-motile). Cultured in the laboratory, L. lactis colonies appear bright orange on nutrient agar. They have a homo-fermentative metabolism and have been reported to produce exclusively L(+) lactic acid. However, reported that D(-) lactic acid can be produced when cultured at low pH. The capability to produce lactic acid is one of the reasons why Lactococcus lactis is one of the most important micro-organisms involved in the dairy industry.
Step 1: Obtaining Mesophilic Culture.
So, we are going to make a mesophilic culture, which means cultivating the Streptococcus Lactis at about 30 C or 86 F for the yanks.
Where do we obtain our raw Gram-positive bacteria you ask? Well, we go where S.L. poops and spits; Cultured Buttermilk, a dive bar where all the bacterium of the Lactis likes to hang. Make sure your cultured buttermilk from your local grocery store has live cultures and hasn't been euthanized via pasteurization. We need live specimen.
Step 2: JAR the SUCKERS in a Warm Spot.
So, you take your carton home and poor two cups worth into a mason jar. This is where things get wild. You leave it out in a warm place. It doesn't have to be exactly 86 F, but it helps the lil' buggers mingle like they are high on ecstacy, and that is what we want.
24hrs later and the lactic acid bacteria should have increased acidity, the by-product naturally produced by S.L. while fermenting lactose, the primary sugar found in milk. As lactic acid is produced by the bacteria, the pH of the milk decreases and casein, the primary protein in milk, precipitates causing the curdling or clabbering of milk. This process makes buttermilk thicker than plain milk.