I want to prepare bacterial media containing Kraft lignin ( dissolved in 0.1 M NaOH). after I autoclave,the lignin gets precipitated. Please suggest how to retain the solubility of lignin in the autoclaved media.
Only the higher molecular weigth fraction is precipitated. If you don't need it, filter it off. http://www.diva-portal.org/smash/get/diva2:8797/FULLTEXT01.pdf
In my opinion, you need to determine if the precipitation is due to reactions under your autoclave condition (Temperature) or faster kinetics. A good control experiment will be to stir continoulsy at different temperature levels without an autoclave while quantifying the amount of precipitate you can recover. Molecular weight distributions can always help you quantify the amount of high molecular weight lignin fraction that is precipitated.
I agree to Olumoye Ajao , as lignin usually tends to polymerize in basic media even under mild conditions. Determination of molecular weight distribution should give answers. Several approaches have been reported in literature to avoid (re)polymerization, thus, to retain solubility like the introduction of capping agents or by applying short reaction times with continuous mode operations.
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