Production of ectoine through a combined process that uses both growing and resting cells of Halomonas salina DSM 5928T

Abstract

Using ectoine-excreting strain Halomonas salina DSM 5928(T), we developed a new process for high-efficiency production of ectoine, which involved a combined process of batch fermentation by growing cells and production by resting cells. In the first stage, batch fermentation was carried out using growing cells under optimal fermentation conditions. The second stage was the production phase, in which ectoine was synthesized and excreted by phosphate-limited resting cells. Optimal conditions for synthesis and excretion of ectoine during batch fermentation in a 10 l fermentor were 0.5 mol l(-1) NaCl and an initial monosodium glutamate concentration of 80 g l(-1) respectively. The pH was adjusted to 7.0 and the temperature was maintained at 33°C. In phosphate-limited resting cells medium, monosodium glutamate and NaCl concentration was 200 g l(-1) and 0.5 mol l(-1), respectively, as well as pH was 7.0. The total concentration of ectoine produced was 14.86 g l(-1), the productivity and yield of ectoine was 7.75 g l(-1) day(-1) and 0.14 g g(-1), respectively, and the percentage of ectoine excreted was 79%. These levels of ectoine production and excretion are the highest reported to date.

Systems metabolic engineering of Corynebacterium glutamicum for production of the chemical chaperone ectoine

“…Though there was detectable growth-associated ectoine production during the batch phase, the predominant fraction of ectoine seemed to be produced by cells during the feeding phase. The finally achieved titer of 4.5 g L -1 already approached to that of currently described industrial production systems [38,39,41]. The C. glutamicum cell factory, however, takes high benefit from the fast growth and vitality.…”

“…The C. glutamicum cell factory, however, takes high benefit from the fast growth and vitality. The excellent performance of the C. glutamicum strain ECT-2 under fed-batch conditions allowed the synthetic cell factory to achieve an overall space-time yield of 6.7 g L -1 ectoine per day which is among the highest productivities reported so far in the literature [38,39,41]. Better performance was, so far, only achieved with H. boliviensis [38], and Chromohalobacter salexigens [41].…”

“…While the bacterial milking procedure is an expedient way to recover ectoine under industrial settings [7,8,20], concerted efforts have recently been made to enhance the efficiency and convenience of its production. These efforts include the use of mutants of H. elongata that hyper-secrete ectoine [36], alternative microbial production strains [33,37-39], modifications of the fermentation and milking procedures [38-42], and attempts to raise production through recombinant DNA techniques employing both pro- and eukaryotic host systems [33,37,43-45]. In particular, attempts are being made to uncouple ectoine production from high osmolarity since the use of high-salinity media in the fermentation process imposes notable constraints on the costs, design, and durability of fermenter systems.…”

Ectoine bio-milking in methanotrophs: A step further towards methane-based bio-refineries into high added-value products

“…For instance, the genus Brevibacterium accumulates 150-160 mg g biomass -1 depending on the specie, while ectoine yields of 155-200 mg g biomass -1 have been recorded in Halomonas sp.. Higher yields can be achieved by genetically modified microorganisms (Escherichia coli DH5α can synthesize up to 400-540 mg g biomass -1 ) [8,11,12,[21][22][23]. Nevertheless, M. alcaliphilum 20Z exhibits a superior environmental performance based on its ability to produce ectoine from dilute CH 4 emissions, with a concomitant mitigation of climate change.…”

“…Thus, H. elongata is initially cultivated at low salinity to produce high density cultures, transferred to a high salinity medium to promote ectoine biosynthesis [10] and finally exposed to a hyposmotic shock to induce the excretion of ectoine from the cell to the cultivation broth, where the product is collected for its downstream purification [8]. Nevertheless, this 4 process is costly due to the need for high quality carbon sources (often glucose, yeast and sodium glutamate), which reduces its cost effectiveness [11,12].…”