A new and efficient method for purification of poly-γ- glutamic acid from high-viscosity fermentation broth

Abstract

Purpose:To devise an efficient strategy for the separation and recovery of high-quality γ-PGA by investigation of the physical properties, pigment properties and microfiltration mode of high-viscosity fermentation broth. Methods: The bacterial strain, Bacillus subtilis 115, was used in this study. The viscosity of the fermentation broth was determined by digital viscometer with spindle SP-2 at 25 o C. The concentrations of glucose and L-glutamate were analyzed with a biosensor equipped with both glucose oxidase and Lglutamate oxidase electrodes. The pigment in the fermentation liquid was scanned with a UV spectrophotometer at wavelength range of 200 -500 nm and was removed using activated carbon. Measurement of IR spectrum was performed using an IR spectrophotometer with KBr pellet. . Results:The results showed that the γ-PGA yield was 35 g/L. The viscosity of the fermentation broth was 1600 mPa.s at the end of the batch fermentation. After 3-fold dilution, the viscosity was reduced to one-fortieth of the original value at 65 °C for 30 min., which allowed effective removal of Bacillus subtilis 115 from the broth. Maximum UV absorption of the pigment was occurred at 260 nm. The pigment was removed by shaking with 0.6 % activated carbon powder at 50 rpm for 20 min, resulting in 88 % decolorization. Concentration with hollow-fiber membrane (MWCO 500,000) resulted in complete removal of residual glucose and glutamic acid from the aqueous solution of γ-PGA. The molecular weight of the γ-PGA was 1095 kDa, and its UV scanning spectrum showed an absorption peak at 216 nm. The decomposition temperature (Td) of the γ-PGA was 312.92 oC. Its IR spectrum was consistent with the presence of carboxyl, hydroxyl, carbonyl and amide groups. Conclusion: An efficient method for the extraction and purification of high-quality γ-PGA from highviscosity fermentation broth.

An in vivo study on Drosophila melanogaster, Artemia salina, and Daphnia magna: Is activated carbon used as a food additive reliable?

“…Activated carbon is also used in the purification of additives such as monosodium glutamate (MSG), glutamic acid, and hydrolyzed vegetable proteins (HVPs), which are commonly used in the food industry (Wang et al, 2017;Kobayashi et al, 2018).…”

Kinetic modelling and process optimization of textile effluent treatment with bacterial gamma polyglutamic acid

“…The optical density of fermented medium was found to be 0.891from which indicated the presence of a spectrum analysis high concentration of γ-PGA.The maximal absorption peaks of γ-PGA were reported as 216 nm from scanning at different continuous wavelengths of 190-340 and 190-800 nm, respectively (Zeng et al, 2012;Chatterjee et al, 2019). The peptide chains that are not attributed for the polymers were confirmed by the absence of peaks at 260-280 nm (Wang et al, 2017).The presence of alpha amino acids namely glutamic acid was confirmed through deep blue color formation which was due to the interaction of ninhydrin molecules that act as an oxidizing agent and react with alpha amino acids to form a deep blue color flocculant activity of γ-PGA (10 mg l ) was reported as 14.53±1.2 1/OD against the kaolin suspension at 550 nm due to the effect of cations and pH in the flocculation process. Cations like calcium, aluminum, ferrous ions, magnesium ions and potassium ions were majorly involved in the ion's neutralization process with flocs formation and the previous report also briefs that maximal flocculant activity (21.4±1.2 1/OD) was found for calcium ions at 10 mM ratio.…”