High bioreactor production and emulsifying activity of an unusual exopolymer by Chromohalobacter canadensis 28

Abstract

Unusual composition of an exopolymer (EP) from an obligate halophilic bacterium Chromohalobacter canadensis 28 has triggered an interest in development of an effective bioreactor process for its production. Its synthesis was investigated in 2‐L bioreactor at agitation speeds at interval 600‐1000 rpm, at a constant air flow rate of 0.5 vvm; aeration rates of 0.5, 1.0, and 1.5 vvm were tested at constant agitation rate of 900 rpm. EP production was affected by both, agitation and aeration. As a result twofold increase of EP yield was observed and additionally increased up to 3.08 mg/mL in a presence of surfactants. For effective scale‐up of bioreactors mass transfer parameters were estimated and lowest values of KLa obtained for the highest productivity fermentation was established. Emulsification activity of EP exceeded that of trade hydrocolloids xanthan, guar gum, and cellulose. A good synergism between EP and commercial cellulose proved its potential exploration as an enhancer of emulsifying properties of trade emulsions. A pronounced lipophilic effect of EP was established toward olive oil and liquid paraffin. Cultivation of human keratinocyte cells (HaCaT) with crude EP and purified γ‐polyglutamic acid (PGA) showed higher viability than control group.

Improved Exopolymer Production by Chromohalobacter canadensis Cultures for Its Potential Cosmeceutical Applications

“…The performed bioreactor experiments revealed an effective production of EP by C. canadensis 28 in continuous cultures at low dilution rates. The EP level in continuous cultures (2.15 mg/mL) is similar to that in batch cultures (2.34 mg/mL) at the same kinetic parameters of the bioreactor [11]. Higher levels in continuous cultures in comparison with batch ones were reported for Lactobacillus delbrueckii ssp.…”

“…Variation in dilution rate did not change the strain growth in the range 0.02-0.05 h −1 ; however, there were significantly changed EP levels and productivity. Similarly, the low effect of the other two bioreactor parameters, agitation speed, and aeration rate on the bacterial growth has been observed while their influence on EP production was significant [11].…”

“…Average production yield of marine EPS is around 1 g/L while industry requires a production yield around 10 g/L [14]. The EP yield reached by C. canadensis 28 in batch cultures above two mg/mL has placed this strain among the best halophilic producers [11]; however, this level is still not enough for development of an industrial process. Exploration of continuous cultivation could be a way for development of an effective EP production at constant conditions avoiding preliminary stages in process run-up like cleaning and sterilization of each new reactor and different phases in cell development.…”

“…Fermentations were conducted in a 5 L jacketed glass reactor (LF-2, Prague, Czech Republic) equipped with a hydrofoil impeller Narcissus (0.05 m diameter) filled with 2.4 L medium at 900 rpm and 1.0 vvm, both determined as the optimal agitation speed and aeration rate, respectively [11]. Dissolved oxygen (DO, %) was provided by injecting filtered air at a flow rate of 2.4 L/min and followed in all runs by InPro 6800/12/320 Mettler Toledo Ingold (Leicester, LE4 1AW, UK) oxygen sensor.…”

“…Following our previous results, cultivation of C. canadensis 28 was performed in an optimal medium for growth and EP production 900 rpm and 1.0 vvm [10,11]. The time course of batch fermentation continued up to the 18th hour of cultivation, when OD 660 of 3.7 (1.7 mg/mL) was measured, pO2 of 75%, then continuous experiments were performed with dilution rate ranging from 0.02 to 0.1 h −1 .…”