Abstract
Cheese whey (CW) can be an excellent carbon source for polyhydroxyalkanoates (PHA)-producing bacteria. Most studies have used CW, which contains high amounts of lactose, however, there are no reports using raw CW, which has a relatively low amount of lactose. Therefore, in the present study, PHA production was evaluated in a two-stage process using the CW that contains low amounts of lactose. In first stage, the carbon source existing in CW was converted into acetic acid using the bacteria, Acetobacter pasteurianus C1, which was isolated from food waste. In the second stage, acetic acid produced in the first stage was converted into PHA using the bacteria, Bacillus sp. CYR-1. Under the condition of without the pretreatment of CW, acetic acid produced from CW was diluted at different folds and used for the production of PHA. Strain CYR-1 incubated with 10-fold diluted CW containing 5.7 g/L of acetic acid showed the higher PHA production (240.6 mg/L), whereas strain CYR-1 incubated with four-fold diluted CW containing 12.3 g/L of acetic acid showed 126 mg/L of PHA. After removing the excess protein present in CW, PHA production was further enhanced by 3.26 times (411 mg/L) at a four-fold dilution containing 11.3 g/L of acetic acid. Based on Fourier transform infrared spectroscopy (FT-IR), and 1H and 13C nuclear magnetic resonance (NMR) analyses, it was confirmed that the PHA produced from the two-stage process is poly-β-hydroxybutyrate (PHB). All bands appearing in the FT-IR spectrum and the chemical shifts of NMR nearly matched with those of standard PHB. Based on these studies, we concluded that a two-stage process using Acetobacter pasteurianus C1 and Bacillus sp. CYR-1 would be applicable for the production of PHB using CW containing a low amount of lactose.
Highlights
The replacement of traditional plastics by bioplastics is gaining interest in the increasing of the sustainability of the polymer industry
To improve the capability of PHA production, we designed a two-stage process: cheese whey (CW) was converted to acetic acid using Acetobacter pasteurianus C1 in the first stage, and, in the second stage, acetic acid produced from CW was converted to PHA using Bacillus sp
The Fourier transform infrared spectroscopy (FT-IR) spectrum of PHB produced by CYR-1 was measured by attenuated total reflection using a Nicolet 6700 FT-IR spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). 1 H (300 MHz) and 13 C (75 MHz) nuclear magnetic resonance (NMR) spectra were recorded on an Oxford
Summary
The replacement of traditional plastics by bioplastics is gaining interest in the increasing of the sustainability of the polymer industry. PHA has been extensively studied as an alternative to petroleum-based plastics [10] It has not yet been in practical use because of its high production cost, primarily owing to the high cost of substrates (11% of the total production cost) that are used for the growth of microorganisms [10]. For this reason, in our previous study, we examined the capability of strain CYR1 in producing PHA using raw CW as a feed stock. The functional groups, primary structure, higher-order structure, and thermal properties of the produced poly-β-hydroxybutyrate (PHB) from the two-stage process were analyzed using Fourier transform infrared spectroscopy (FT-IR), 1 H 13 C nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA), respectively
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