Effect of the oxygen supply on pattern of growth and corrinoid and organic acid production of Propionibacterium shermanii

Propionibacterium shermanii CDB 10014 is able to grow even at high oxygen transfer rates (24.0 mmol O₂ l⁻¹ h⁻¹), in contrast to reports in the specialised literature, where all Propionibacteria are considered oxygen-sensitive microorganisms. Propionic acid is the main product in anaerobiosis. The presence of oxygen in the system leads to an inhibition of propionic acid production while acetic acid formation is enhanced. At high oxygen supply rates no propionic acid is produced and acetic acid is the main product. Lactic acid is also produced in reasonable quantities (2.7 g l⁻¹). The growth rate (μ_max) is higher in anaerobiosis (0.19 h⁻¹) than in aerobiosis (0.12–0.15 h⁻¹). The cell yield is higher in aerobiosis (0.18–0.22 g g⁻¹) than in anaerobiosis (0.14 g g⁻¹) suggesting the oxidative metabolism of glucose by Propionibacterium shermanii CDB 10014. No corrinoid production was detected at oxygen transfer rates of more than 13.6 mmol l⁻¹ h⁻¹. Received: 10 September 1997 / Received revision: 6 January 1998 / Accepted: 9 January 1998     

Comparison of methods for determination of vitamin B12 in microbial material

Three different methods for the measurement of vitamin B12 were compared: two spectrophotometric methods and an HPLC one. When the pure vitamin was used, the results obtained using all three methods were similar, but when samples from microbial material were used, the results were different. The HPLC method could distinguish the true vitamin B12 from the different vitamin B12 analogues whereas the spectrophotometric methods could not.     

Effect of oxygen supply on biomass,organic acids and vitamin B12 production by Propionibacterium shermanii

Propionibacterium shermanii CDB 10015 was able to grow at different volumetric oxygen transfer coefficients (KLa) of 10, 22, 53h–1. These results demonstrate that this bacterium, known as anaerobic, is able to grow well under aerobic conditions. The cell biomass increased from 7.9 in anaerobic conditions to 18.3g/l at KLa 53h–1, increasing also the cell yield from 0.3 to 0.7g/g. The organic acid production pattern also changed with aeration. The acetic: propionic acid ratio increased from 0.38 in anaerobiosis to 6.25 at KLa 53h–1. The vitamin B12 production decreased from 3.1mg/l in anaerobiosis to 0.5mg/l at KLa 53h–1.     

Oxygen transfer on β- D-galactosidase production by Kluyveromyces marxianus using sugar cane molasses as carbon source

The optimal initial volumetric oxygen transfer coefficient (K_La) was 60 h^–1 for the production of -d-galactosidase from Kluyveromyces marxianus CDB 002, using sugar cane molasses as carbon source. At this K_La applying an agitation/aeration relationship of 700 rpm/0.66 vvm resulted in 812 U l^–1 h^–1 for -d-galactosidase production. This was about 50% better than a relationship of 500 rpm/2 vvm at the same K_La.     

One step partial purification of β-D-galactosidase from Kluyveromyces marxianus CDB 002 using STREAMLINE-DEAE

The intracellular enzyme -D-galactosidase provides interesting applications in the dairy industry, which are able to solve problems related to product processing, or can alleviate lactose intolerance in some populations. In order to obtain a technical enzyme, yeast cells of Kluyveromyces marxianus CDB 002 were disrupted by high pressure homogenization and an innovative chromatographic technique was tested for the recovery of -D-galactosidase. A STREAMLINE 25 column, containing 65 ml STREAMLINE-DEAE was equilibrated with 50 mM potassium phosphate buffer pH 7.5 at an upward flow of 250 cmh^–1. 100–200 ml cell homogenate were applied onto the expanded gel. After unbound proteins and cellular debris were washed out, the bed was allowed to sediment and -D-galactosidase was eluted with a downward flow of 0.2 M NaCl in the same buffer. A 6-fold purification factor was achieved with 63% activity recovery, while removing cell debris at a single step, thus avoiding a centrifugation step. Concentration and volume of the applied sample affected purification and gel performance. The results presented show STREAMLINE-DEAE chromatography to be an interesting method for the production of -D-galactosidase as a technical enzyme, since it can also be applied on a large scale without much modification.     

Formulation of a lactose-free, low-cost culture medium for the production of β- D-galactosidase by Kluyveromyces marxianus

A lactose-free, low-cost culture medium for the production of -d-galactosidase by Kluyveromyces marxianus was formulated. At high aeration rates (2.2 vvm) and concentrations of 100 g sugar cane molasses l^–1 as carbon source and 100 g corn steep liquor l^–1 as vitamin and nitrogen source an enzyme production of 708 U l^–1 h was achieved. This was 20% higher than using a medium that contained lactose which is considered the primary inductor of -d-galactosidase synthesis.