Nypa fruticans fronds Wickerhamomyces anomalus alkaline hydrogen peroxide alkali–heat pretreatment bioelectricity biomass crystallinity biomass densification biomass sample cacao beans cacao fruit cacao husk cacao mucilage exudate cacao placenta cellulose condensed tannins electricity empirical correlation feature reduction functional groups for energy storage gas chromatography with mass selective detection (GC-MS) generation genotypes granulometric distribution heat capacity high-performance liquid chromatography (HPLC) hydrophobic agent liquefaction microbial fuel cell microbial fuel cells onion