Optimization of the growth and α-amylase production of Bacillus subtilis IP 5832 in shake flask and laboratory fermenter batch cultures

Abstract

Cell growth and the level of α-amylase in response to the carbon and nitrogen sources used for the growth of the strain Bacillus subtilis IP 5832 were examined. Based on the amylase productivity level in shake flask cultures after 24 hours of growth, the growth medium containing starch and peptone was selected as the best medium. Amylase production was greatly reduced when glutamate or citrate as sources of carbon were used. Experiments performed at different initial concentrations of starch showed that although the strain grew well with all the starch concentration used, 0.5 % starch was necessary for maximum α-amylase production, inducing 1.55 IU mL-1 of amylase to be secreted after 8 h of cultivation in shaking flasks. During the batch fermentation of B. subtilis IP 5832 strain in 2 L laboratory fermenter, a 60% higher activity (2.5 IU mL-1) was obtained. The production of the enzyme was directly related to the growth of the strain. Maximum enzyme activity was obtained at the beginning of the stationary growth phase.

Ćelijski rast i nivoi α-amilaze nakon gajenja Bacillus subtilis IP 5832 ispitivani su u zavisnosti od različitih izvora ugljenika i azota korišćenih u podlozi. Na osnovu produktivnosti amilaze nakon dvadesetčetvoročasovnog gajenja kulture u erlenmajerima sa mešanjem pokazano je da je najbolja hranljiva podloga ona koja sadrži skrob i pepton. Kada su glutamat ili citrat korišćeni kao izvori ugljenika produkcija enzima je bila značajno redukovana. Eksperimentima u kojima je varirana inicijalna koncentracija skroba pokazano je da je, iako soj dobro raste na svim korišćenim koncentracijama, 0,5 % skrob neophodan za maksimalnu produkciju enzima, indukujući sekreciju 1,55 IU mL-1 amilaze nakon 8 sati gajenja kulture u erlenmajerima sa mešanjem. Tokom šaržne fermentacije B. subtilis IP 5832 soja u laboratorijskom fermentoru od 2 L dobijeno je 60 % više aktivnosti enzima (2,5 IU mL -1). Produkcija enzima je bila direktno vezana za rast mikroorganizma. Maksimalna enzimska aktivnost dobijena je na početku stacionarne faze rasta.