Assessment of Relevant Factors Influencing Lipolytic Enzyme Production by Thermus thermophilus HB27 in Laboratory‐Scale Bioreactors

Abstract

Nowadays, there is not much information on the large-scale production of thermostable lipolytic enzymes by thermophilic organisms. Therefore, in this study the lipolytic enzyme production by Thermus thermophilus HB27 in laboratoryscale bioreactors was undertaken. In order to determine the most suitable bioreactor, two configurations were investigated: stirred-tank and airlift bioreactor. It was demonstrated that the stirred-tank configuration led to the highest lipolytic extracellular activities, about 2.3-fold higher than those found in the corresponding cultivation in the airlift bioreactor. On the other hand, the influence of several factors such as culture nutrients concentration, aeration, and agitation rate on the production of thermophilic lipolytic enzymes in a 5-L stirred-tank bioreactor was assayed. At reduced nutrients concentration (50 % with respect to the basal medium), a higher product/biomass yield was attained, without any operational problems. From the relationship between mass transfer coefficient (K L a), aeration, and agitation rates it was concluded that there is a lesser dependence on the aeration than the agitation rate. In addition, the mechanical stirring of the bioreactor could tear the membranes that contain the rotund bodies often found in cultures of thermophilic microorganisms, thus increasing the extracellular enzyme production.

Insights into polyaromatic hydrocarbon biodegradation by Pseudomonas stutzeri CECT 930: operation at bioreactor scale and metabolic pathways

“…This behaviour is coincident with what was found in other biological processes devoted to the degradation of dyes or to the production of metabolites (Deive et al 2009(Deive et al , 2010.…”

Scaling-up the production of thermostable lipolytic enzymes from Thermus aquaticus YT1

“…Additionally, it is observed that higher agitation rates involve higher extracellular and membrane-bound lipolytic activity to the detriment of intracellular enzyme, while no significant variations in enzyme distribution are recorded when increasing the aeration. That means a greater effect of the agitation, a trend also highlighted by Deive et al [12] for other Thermus strain. This fact can be explained in the light of the hydrodynamic setting existing inside the bioreactor, leading to mechanical stress phenomena.…”

“…No remarkable differences are observed when perfluorodecalin is added to the culture medium. In all cases, there are multicellular bodies in which multiple cells are grouped and surrounded by a membrane, as described by Castán et al [41] and Deive et al [12] when researching other Thermus strains. It is outstanding that in this case, the membranes surrounding the multicellular bodies are broken, thus indicating some cell damage is already occurring at the cultivation at flask scale, even in the case where no perfluorodecalin is added.…”

“…Factors such as agitation-aeration, pH and temperature, as well as culture medium composition, exert a relevant influence on the production of lipases. Previous studies on lipolytic enzymes production by other thermophilic strains indicated that the process was strongly affected by cultivation variables, such as the mineral content of the culture medium and the degree of aeration amongst others [11][12][13][14]. However, the effects of operating variables on the production of microbial metabolites are strongly strain dependent, and it remains to be ascertained if T. aquaticus YT1 might show a similar behaviour to other Thermus strains.…”

“…This factor has previously been considered to be crucial for favouring mixing and oxygen transfer in the culture medium [12]. Therefore, 700 rpm and 0.17 vvm are the conditions maximizing the lipolytic synthesis, amongst those studied in the present work.…”