Background
Pineapple is the third most important tropical fruit produced worldwide, and approximately 24.8 million tons of this fruit are produced annually throughout the world, including in Thailand, which is the fourth largest pineapple producer in the world. Pineapple wastes (peel and core) are generated in a large amount equal to approximately 59.36% based on raw material. In general, the anaerobic digestion of pineapple wastes is associated with a high biochemical oxygen demand and high chemical oxygen demand, and this process generates methane and can cause greenhouse gas emissions if good waste management practices are not enforced. This study aims to fill the research gap by examining the feasibility of pineapple wastes for promoting the high-value-added production of biodegradable polyhydroxybutyrate (PHB) from the available domestic raw materials. The
Conclusions
This study demonstrated the feasibility of utilizing pineapple waste products from the canned pineapple industry as lignocellulosic feedstocks for PHB production. C. necator strain A-04 was able to grow on various sugars and tolerate levulinic acid and 5-hydroxymethyl furfural, and a detoxification step was not required prior to the conversion of cellulose hydrolysate to PHB. In addition to acid hydrolysis, CAE was identified as a potential carbon source and offers a novel method for the low-cost production of PHB from a realistic lignocellulosic biomass feedstock.
Results
The results indicated that pretreatment with an alkaline reagent is not necessary. Pineapple core was sized to - 20/+ 40 mesh particle and then hydrolyzed with 1.5% (v/v) H2SO4 produced the highest concentration of fermentable sugars, equal to 0.81 g/g dry pineapple core, whereas pineapple core with a + 20 mesh particle size and hydrolyzed with 1.5% (v/v) H3PO4 yielded the highest concentration of PHB substrates (57.2 ± 1.0 g/L). The production of PHB from core hydrolysate totaled 35.6 ± 0.1% (w/w) PHB content and 5.88 ± 0.25 g/L cell dry weight. The use of crude aqueous extract (CAE) of pineapple waste products (peel and core) as a culture medium was investigated. CAE showed very promising results, producing the highest PHB content of 60.00 ± 0.5% (w/w), a cell dry weight of 13.6 ± 0.2 g/L, a yield ( YP/SYP/S<math><msub><mi>Y</mi><mrow><mi>P</mi><mrow><mo>/</mo></mrow><mi>S</mi></mrow></msub></math> ) of 0.45 g PHB/g PHB substrate, and a productivity of 0.160 g/(L h). Conclusions: This study demonstrated the feasibility of utilizing pineapple waste products from the canned pineapple industry as lignocellulosic feedstocks for PHB production. C. necator strain A-04 was able to grow on various sugars and tolerate levulinic acid and 5-hydroxymethyl furfural, and a detoxification step was not required prior to the conversion of cellulose hydrolysate to PHB. In addition to acid hydrolysis, CAE was identified as a potential carbon source and offers a novel method for the low-cost production of PHB from a realistic lignocellulosic biomass feedstock.