The effects of sulfate concentration and COD/S ratio on the anaerobic degradation of butyrate were investigated by using 2.0 L anaerobic chemostat-type reactor at 35°C. The study was conducted over a wide range of the COD/S ratio (1.5 to 148) by varying COD concentrations (2500–10000 mg/L) and sulfate concentrations (68–1667 mg-S/L) in the substrate. The sludge retention time at each COD/S ratio was changed from 5 to 20 days. The interaction between methane producing bacteria (MPB) and sulfate-reducing bacteria (SRB) was evidently influenced by COD/S ratio in the substrate. When COD/S ratio was 6.0 or more, methane production was the predominate reaction and over 80% of the total electron flow was used by MPB. At the COD/S ratio of 1.5, SRB utilzed over 50% of the total electron flow. A large amount of sulfate reduction resulted in not only the decrease of methane production, but also the rapid increase of the bacterial growth. The degradation pathway of butyrate and the composition of bacterial populations in the reactor were also dominated by COD/S ratio. In sulfate depleted condition, butyrate was degraded to methane via acetate and hydrogen by MPB. On the other hand, butyrate was firstly degraded into sulfide and acetate in sulfate rich conditions by SRB, and the produced acetate was then degraded by acetate consuming MPB and SRB. The methanogenesis from acetate was inhibited by the high concentration of sulfide.

Pineapple leaf fibre (PALF) is major waste from pineapple cultivation with high cellulose content that exhibits superior mechanical properties. In this study, chemical-mechanical treatments were conducted to produce cellulose and microcellulose. For alkali and steam treatment, PALF treated with 5 wt% sodium hydroxide solution and steamed in an autoclave at temperature of 121 °C and pressure of 21 psi. Next, the PALF was bleached with 5 wt% sodium chlorite. Continued with acid hydrolysis with 3.5 M and 7.5 M hydrochloric acid to produce cellulose. For, the mechanical treatment which involved homogenization and ultrasonication to produce the microcellulose, the ultrasonication was varied for 30 and 60 min. The samples were analysed by Scanning Electron Microscopy, Thermal Gravimetric Analysis and Fourier Transform Infrared Spectroscopy (FTIR) to study surface morphology, thermal stability and functional group respectively. The results showed that ABAHU60 with alkali treatment, bleaching, acid hydrolysis, homogenization and ultrasonication of 60 min exhibits excellent thermal stability and surface morphology, where the maximum degradation temperature occurs at 349 °C, which is a 5% improvement compare to untreated fibre. Its surface is smoother without impurities, with a loose structure and reduce diameter of fibre.

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