Monday 31 July 2017

Combination of food wastes for an efficient production of nisin in realkalized fed-batch cultures

Biochemical Engineering Journal

Nisin production by Lactococcus lactis CECT 539 was studied in four realkalized fed-batch cultures in diluted whey with feeding with lactose- and glucose-containing substrates. The first and third cultures were fed with mixtures of whey (W) and a 400 g/L concentrated glucose (CG), or with a concentrated mussel processing waste (CMPW) and CG, respectively.
The second and fourth cultures were respectively performed under the same conditions as in the first and third fermentations. However, these cultures were supplemented with mixtures of W plus a 2% (w/v) yeast extract (WYE2) and CG (second culture), or with CMPW plus a 2% (w/v) yeast extract (CMPWYE2) (fourth culture) after sample extractions at 132 and 168 h, respectively. From these times, each culture was fed with mixtures of WYE2 and CG, or CMPWYE2 and CG, respectively.
The final concentrations of nisin obtained in the third (223.98 BU/mL) and fourth (350.61 BU/mL) cultures, fed with glucose-containing substrates (CG and CMPW), were considerably higher than those obtained in the first (108.00 BU/mL) and second (158.53 BU/mL) cultures fed with the mixture of lactose- and glucose-containing substrates (W and CG).

Sunday 30 July 2017

High hydrostatic pressure as pretreatment and adjuvant for the enzymatic release of ferulic acid from corn cob

Process Biochemistry

Bioprocesses based on the use of enzymes can be employed for the obtainment of ferulic acid by its solubilization from corn cob, which is a natural source of this phenolic compound. In order to overcome the limitations caused by the recalcitrance of biomass, the application of pretreatments is advisable. The utilization of high hydrostatic pressure on the enzymatic release of ferulic acid from corn cob with three feruloyl esterase extracts was studied applying pressurization at 600 MPa as a pretreatment in combination with a mild thermal treatment at 130 °C/2 h. Additionally, pressurization at 200 MPa during the enzymatic hydrolysis step was assessed to increase the ferulic acid yield. The results showed that the application of a high pressure pretreatment at 600 MPa/40 °C/15 min to thermally treated corn cob increased by 20% the ferulic acid release in comparison with the thermal treatment for Ultraflo® L, but not for the Aspergillus extracts. Pressurization at 200 MPa during the hydrolysis stage affected differently the enzymes stability and ferulic acid release depending on the extract and the pretreatments applied, showing that the effects of pressurization are complex and must be assessed in each case.