Inexpensive Production of Poly (3‑hydroxybutyrate‑co‑ 3‑hydroxyvalerate) from Bacillus megaterium PP-10 Using Pineapple Peel Waste

Abstract

Pineapple peel waste has recently been interested in being utilized as a low-cost carbon source in PHA biosynthesis to reduce the production cost of PHA. The production of copolymer Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [PHBV] by the new Bacillus megaterium PP-10 was investigated. The bacteria were grown in a mixture of pineapple peel hydrolysate (PPH) and 3-hydroxyvalerate (3HV) precursor such as sodium propionate or sodium valerate at ratios of 1:1. Remarkably, the microbial growth and PHBV production in a mixture of PPH and sodium valerate exhibited higher biomass and higher PHA amount than that of sodium propionate, accounted about 2.40 ± 0.07 g/L of DCW and 0.71 ± 0.03 g/L of PHA concentration (PHA content of 29.6%DCW). Moreover, to control the 3HV molar fraction in PHBV, various sodium valerate concentration from 2 to 18 g/L was supplemented with PPH, and the result showed that the 3HV fraction increased linear trend with an increase in valerate concentration and was in the range between 6-35 mol%HV. In contrast, a maximum PHA concentration of 1.65 ± 0.04 g/L content (about 49%DCW) was obtained when B. megaterium PP-10 was cultivated in 18 g/L of total reducing sugar in PPH with 2 g/L of sodium valerate at 12 h of cultivation. Finally, the produced PHBV containing 20 mol%HV was further determined by some thermal properties and found that it possessed the melting and glass transition temperatures of 148°C and -10°C, respectively. Therefore, PHBV synthesized by B. megaterium PP-10 with various 3HV fractions was an excellent choice for biopolymer production.