Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Solid-state fermentation of coffee pulp with Aspergillus tamarii V12307 was carried out in laboratory scale reactors (bottle and column) to evaluate the effect of four different mixing frequencies (2.0, 2.7, 4.0 and 8.0 day^–1) on fungal growth, indirectly determined by carbon dioxide formation and the production of spores and pectin methylesterase. Coffee pulp was used as the sole source of nutrients. An increase in the fraction of bonded particles was observed in the bottle reactors after 12 h of cultivation when no mixing was applied. The use of any mixing frequency reduced the fraction of bonded particles. However, there was no significant difference in pectin methylesterase production between the mixing
frequencies at the end of the fermentation. Similarly, there were no significant differences in CO2 production, oxygen uptake or sporulation, demonstrating that the mycelium was not damaged by intermittent mixing. This strategy of mixing could be used in large scale reactors in order to reduce heat and mass limitations.Fermentacija otpada nastalog pri proizvodnji kave s pomoću plijesni Aspergillus tamarii V12307 provedena je u laboratorijskim reaktorima (bocama i kolonama), te je ispitan utjecaj četiriju frekvencija miješanja (2,0; 2,7; 4,0 i 8,0 dan-1) na rast plijesni, i to indirektno, tj. mjerenjem proizvodnje ugljičnog dioksida, spora i pektin metilesteraze. Otpad nastao pri proizvodnji kave upotrijebljen je kao jedini izvor hranjiva. Povećanje udjela vezanih čestica primijećeno je nakon 12 sati uzgoja u bocama bez miješanja. Miješanje je smanjilo udjel vezanih čestica, ali nije bitno utjecalo na proizvodnju pektin metilesteraze. Također nije utjecalo na proizvodnju CO2, potrošnju kisika ili sporulaciju, što znači da povremeno miješanje supstrata nije oštetilo micelij plijesni. Takvim se miješanjem mogu smanjiti ograničenja u prijenosu topline i mase u industrijskim reaktorima
