Upotreba koncentrata dušika iz krumpira u proizvodnji α-amilaze s pomoću plijesni Aspergillus oryzae

The influence of various nitrogen sources and media supplements on α-amylase (EC 3.2.1.1) formation by Aspergillus oryzae ATCC 1011 was investigated in shake flask experiments and batch fermentations. Both inorganic and organic nitrogen-containing supplements have been applied, while corn starch and ammonium sulphate were used as the major source of carbon and nitrogen, respectively. Shake flask experiments revealed that potato nitrogen concentrate (PNC) is almost equivalent to corn steep liquor (CSL) in supporting amylase formation. A pretreatment step consisting of clarification of the turbid material did not show any significant effect. The replacement of the inorganic nitrogen source by sodium nitrate led to lower enzyme yields. Other complex supplements may reduce the enzyme level formed, e.g. casein hydrolysate, or increase the amylase titre slightly, e.g. yeast extract or malt extract. Cultivations in instrumented bench top reactors on media supplemented with PNC led to higher cell growth rates and yields of α-amylase in comparison with the medium without any supplement. Replacement of PNC by CSL revealed a slightly increased enzyme level, which is in the range of 9–17 % after 100 h of cultivation. Only minor differences were revealed in the growth kinetics and enzyme formation when PNC was used as the sole nitrogen source, replacing a mixture of soybean meal, yeast extract, malt extract and casein hydrolysate in bioreactor cultivations with lactose as the carbon source. However, metabolic differences as seen from the course of dissolved oxygen tension (DOT), α-amino nitrogen concentration and the amount of acid needed to maintain a constant pH were observed.Istražen je utjecaj različitih izvora dušika i dodataka podlozi na proizvodnju α-amilaze (EC 3.2.1.1) s pomoću plijesni Aspergillus oryzae ATCC 1011 u pokusu na tresilici i šaržnim uzgojem. Primijenjeni su anorganski i organski dušikovi spojevi, a kao glavni izvori ugljika i dušika korišteni su kukuruzni škrob i amonijev sulfat. Pokusima na tresilici dokazano je da je utjecaj koncentrata dušika iz krumpira (potato nitrogen concentrate – PNC) na proizvodnju amilaze skoro jednak onom ekstrakta kukuruza (corn steep liquor – CSL). Pročišćavanjem zamućenog materijala prije obrade nije se postigao značajan učinak. Zamjenom anorganskog izvora dušika natrijevim nitratom dobiveni su manji prinosi enzima. Dodatkom drugih kompleksnih spojeva, kao što je hidrolizat kazeina, smanjio se prinos enzima, a dodatkom ekstrakta kvasca ili slada neznatno se povećao titar amilaze. Veći rast stanica i bolji prinos α-amilaze postignut je uzgojem na podlozi obogaćenoj s PNC u reaktoru na postolju nego bez tih dodataka. Zamjenom PNC sa CSL postignuto je povećanje prinosa enzima za 9-17 % nakon 100 sati uzgoja. Upotreba PNC kao jedinog izvora dušika, uz zamjenu sojine kaše, ekstrakta kvasca i slada te hidrolizata kazeina laktozom kao izvorom ugljika, dovela je do neznatnih razlika u kinetici rasta i formiranju enzima u bioreaktoru. Međutim, uočene su metaboličke razlike u zasićenosti otopljenim kisikom (dissolved oxygen tension – DOT), koncentraciji α-amino dušika i količini kiseline potrebne za održavanje konstantnog pH

Use of Potato Nitrogen Concentrate in the Production of α-Amylase by Aspergillus oryzae

The influence of various nitrogen sources and media supplements on α-amylase (EC 3.2.1.1) formation by Aspergillus oryzae ATCC 1011 was investigated in shake flask experiments and batch fermentations. Both inorganic and organic nitrogen-containing supplements have been applied, while corn starch and ammonium sulphate were used as the major source of carbon and nitrogen, respectively. Shake flask experiments revealed that potato nitrogen concentrate (PNC) is almost equivalent to corn steep liquor (CSL) in supporting amylase formation. A pretreatment step consisting of clarification of the turbid material did not show any significant effect. The replacement of the inorganic nitrogen source by sodium nitrate led to lower enzyme yields. Other complex supplements may reduce the enzyme level formed, e.g. casein hydrolysate, or increase the amylase titre slightly, e.g. yeast extract or malt extract. Cultivations in instrumented bench top reactors on media supplemented with PNC led to higher cell growth rates and yields of α-amylase in comparison with the medium without any supplement. Replacement of PNC by CSL revealed a slightly increased enzyme level, which is in the range of 9–17 % after 100 h of cultivation. Only minor differences were revealed in the growth kinetics and enzyme formation when PNC was used as the sole nitrogen source, replacing a mixture of soybean meal, yeast extract, malt extract and casein hydrolysate in bioreactor cultivations with lactose as the carbon source. However, metabolic differences as seen from the course of dissolved oxygen tension (DOT), α-amino nitrogen concentration and the amount of acid needed to maintain a constant pH were observed