Colonizing a lambic pulque

I started up a pulque (agave nectar sugar based alchohol) last week. I left the fermentation chamber open to the environment to try and encourage a natural microbe succession. After a week I had no noticeable growth or odor change. I added diammonium phosphate as agave nectar is lacking in nutrient beside sugar. I eventually left milk out overnight as primary milk colonizers are lactic acid bacteria, and I added ~20ml of the milk to my 1 gallon batch.

Any suggestions on starting up a natural colonization for future batches?
Also used orange peel and sassafras root as flavorings, could this have inhibited growth?

Well if you really wanted to emulate lambic producers, you would leave it out overnight and then dump it into a recently used, minimally cleaned fermenter and let those microbes inoculate your pulque…

As far as starting a spontaneous inoculation, it kind of depends on what kinds of microbes you’re targeting. Leaving something out in the environment tends to favor bacteria and mold, which is why this is generally done when nighttime temperatures are in the 40F range or below to discourage mold, and the wort is highly hopped to discourage the LAB from dominating before yeast can begin fermentation. I can’t imagine that the orange peel or sassafras root are very anti-microbial, so that probably isn’t the problem.

The safest way to do this is to leave out several jars of whatever medium you are using in different locations. Think of the places that yeast will hang out, such as by fruit trees, although yeast really can be found anywhere. Having more than one jar increases your chances of getting something useable. After a good time period, say 8 hours or so, transfer it to an airlocked container to minimize further oxygen exposure to discourage mold and see if anything starts. Once you have something useful, then add it back to your pulque must.

Adjusting pH to 4.5 or below will reduce the likelihood of spoilage bacteria taking hold, while still allowing the LAB to grow. Also, if you make your own pickles or sauerkraut, the brine from a fermenting batch is a great source of natural LAB. This is much less likely to make you sick than leaving milk out overnight…