RESEARCH ON THE IMPACT OF THE AIR-LIQUID JET MIXER UPON RING BIOREACTOR OPERATION

In the production of biological preparations for agriculture there are promising jet bioreactors with an external circulation ring, providing intense mixing of the medium along with a high degree of aeration. However, application of these bioreactors is limited by large shear loads on the microorganisms (microorganism cells) arising in the circulation pump. The article deals with one of the ways for solving this problem by using a low-capacity pump for the circulation of the fermentation medium according to a non-standard scheme of medium jet aeration in order to intensify the mass exchange processes. There are presented results of physical simulation of the mixing parameters of flows in an aerator-jet mixer and their impact upon the intensity of metabolic processes in the circulation ring of a bioreactor.

Optimised Production and Extraction of Astaxanthin from the Yeast Xanthophyllomyces dendrorhous

Currently, astaxanthin demand is fulfilled by chemical synthesis using petroleum-based feedstocks. As such, alternative pathways of natural astaxanthin production attracts much research interest. This study aimed at optimising bioreactor operation parameters for astaxanthin production and evaluating strategies for its subsequent extraction. The effect of pH and agitation was evident, as a significant reduction in both biomass and astaxanthin production was observed when the culture pH was not controlled and a low agitation speed was applied. At controlled pH conditions and a high agitation speed, a significant increase in biomass (16.4 g/L) and astaxanthin production (3.6 mg/L) was obtained. Enzymatic yeast cell lysis using two commercial enzymes (Accellerase 1500 and Glucanex) was optimised using the central composite design of experiment (DoE). Accellerase 1500 led to mild cell disruption and only 9% (w/w) astaxanthin extraction. However, Glucanex treatment resulted in complete astaxanthin extractability, compared to standard extraction method (DMSO/acetone). When supercritical CO2 was employed as an extraction solvent in Accellerase-pre-treated Xanthophyllomyces dendrorhous cells, astaxanthin extraction increased 2.5-fold. Overall, the study showed that extraction conditions can be tailored towards targeted pigments present in complex mixtures, such as in microbial cells.

Increase in the efficiency of removal of iron ions from wastewater by aquatic plant ‘Lemna minor‘

Wastewater from food production enterprises could have significant concentrations of total iron that must be decreased. Aquatic macrophytes, for example ?Lemna genera?, have a high potential for iron ions removal, but kinetics and treatment parameters should be qualified. The aim of the work is to increase in the efficiency of removal of iron ions from wastewater in the process of biological wastewater treatment using ?Lemna minor? and to determine rational parameters of the treatment (biomass, process duration, hydraulic load). The kinetics of the removal of iron ions from the water was studied in the batch mode of a biological reactor operation under various biomass quantities. Verification of the obtained rational parameters of the process was carried out under continuous mode conditions. The results obtained from the kinetics of the batch mode the bioreactor operation process indicate an increase in the degree of removal of ferrous ions from wastewater from 61.0% to 91.7% with an increase in the plant biomass concentration from 8 mg/L to 25 mg/L during the wastewater treatment process of 24 hours. The rational parameters of removal of iron ions from wastewater in the batch mode of the bioreactor operation are determined: biomass of duckweed is 25 mg/L; the treatment process duration is 8 hours; the hydraulic load is 0,126 L/(h?L). The purification effect was 89.8%.