Dark fermentation of pretreated hydrolysates of pineapple fruit waste for the production of biohydrogen using bacteria isolated from wastewater sources

ABSTRACT

In the present study, both acidic and alkaline hydrolysate of pineapple waste was utilised for the production of biohydrogen using locally isolated bacterial strains. The bacteria were isolated from different wastewater sources and were identified as Proteus mirabilis, Pseudomonas aeruginosa, Bacillus altitudinus, Bacillus subtilis, Paenibacillus alvei, and Lysinibacillus sphaericus. Experimental results showed that the highest biohydrogen yield of 836.33 ± 48.02 mL H₂ was produced from alkaline hydrolysate with Bacillus altitudinis during the 96^thhr of fermentation. Among the different bacterial strains, B. altitudinis showed higher H₂ production. Comparatively alkaline hydrolysates exhibited a higher yield of hydrogen than acidic hydrolysates. The final pH of the experiment was found to be in acidic range. The total VFA concentration ranged between 930 ± 207.85 mg/L to 3050 ± 476.97 mg/L. Both sugar degradation and COD reduction were more than 80% in the acidic and alkaline hydrolysates while the lowest sugar degradation and COD reduction were observed for the untreated biomass. The rationale behind this study was to convert the waste biomass into energy by utilising the potential of native bacterial communities.

GRAPHICAL ABSTRACT

KEYWORDS:

• Biohydrogen
• pineapple waste
• acid pretreatment
• alkali pretreatment
• dark fermentation
• Bacillus altitudinis

Acknowledgement

The author ((JM)is thankful to Kerala State Council for Science Technology and Environment (KSCSTE), Govt. of Kerala, India for providing research fellowship. The authors are thankful to the Inter-University Instrumentation Centre (DST-SAIF & DST-FIST, Govt. of India) and School of Environmental Sciences, MGU (KSCSTE-SARD, VERC Project, Govt. of Kerala) for providing the instrumentation facility. The support and inspiration of Dr. A.P. Thomas (Director, ACESSD) and Dr. C.T. Aravindakumar (Professor, SES MGU) are greatly acknowledged here.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the [and/or] its supplementary materials.

Additional information

Funding

This work was partially supported by Kerala State Council for Science Technology and Environment (KSCSTE), Govt. of Kerala, India.