Potential use of Bacillus paramycoides for the production of the biopolymer polyhydroxybutyrate from leftover carob fruit agro-waste

Leila Djerrab; Zohra Chekroud; Amer Rouabhia; Mohamed Abdesselem Dems; Imane Attailia; Luis Isidoro Romero Garcia; Mustapha Adnane Smadi

doi:10.3934/microbiol.2022023

Potential use of Bacillus paramycoides for the production of the biopolymer polyhydroxybutyrate from leftover carob fruit agro-waste

AIMS Microbiol. 2022 Aug 8;8(3):318-337. doi: 10.3934/microbiol.2022023. eCollection 2022.

Authors

Leila Djerrab¹, Zohra Chekroud², Amer Rouabhia³, Mohamed Abdesselem Dems⁴, Imane Attailia⁵, Luis Isidoro Romero Garcia⁶, Mustapha Adnane Smadi⁷

Affiliations

¹ Laboratory of Research on the Physical Chemistry of Surfaces and Interfaces (LRPCSI), University 20 Août 1955 Skikda, Algeria.
² Research Laboratory of Interactions, Biodiversity, Ecosystems and Biotechnology (LRIBEB) University 20 Août 1955 Skikda, Algeria.
³ Research Laboratory of Biological Treatment of Residues, Department of Chemical Engineering and Food Technology, Institute of Vitivinicultural and Agri-food Research (IVAGRO), University of Cadiz, Spain.
⁴ Bioinformatics and Biostatistics Unit (BIBSU), National Center for Biotechnology, Constantine, Algeria.
⁵ Superior School of Food Sciences and Agro Food Industries (ESSAIA), Algiers, Algeria.
⁶ Director Laboratory of Biological Treatment of Residues, Department of Chemical Engineering and Food Technology University of Cadiz, Spain.
⁷ Laboratory of Animal Biotechnologies, National Center for Biotechnology, Constantine, Algeria.

Abstract

This study was designed to investigate, at a laboratory scale, the possibility of valorizing the leftover carob fruits to produce the eco-friendly biopolymer polyhydroxybutyrate (PHB) by using the bacterial strain Bacillus paramycoides, which has been isolated from the botanical garden of Skikda University in Algeria. The PHB production was tested under various conditions: a pH of 3-8, temperature range of 30-44 °C, carob extracted molasses concentration of 2-8% v/v, an incubation time of 24-96 h and an agitation speed of 150-300 rpm. The effects of different nitrogen sources and carob extracted molasses treatment types were also investigated. The PHB concentration was determined quantitatively as crotonic acid by measuring the absorbance at 300 nm. Cell growth was quantified by measuring the density of the culture at 600 nm. The presence of PHB was confirmed by applying high-performance liquid chromatography (HPLC) using an Aminex HPX-87H and implementing gas chromatography analysis. The best yield of PHB synthesis was obtained by using 6% v/v of 5 M H₂SO₄ treated with carob molasses as a carbon source, with peptone as a nitrogen source; incubation was conducted at 37 °C for 96 h at an agitation speed of 300 rpm (114.95 mg/L). The HPLC analysis confirmed the synthesis of PHB by B. paramycoides to have a chromatogram retention time of 22.5 min. Carob waste was successfully valorized to PHB.

Keywords: Bacillus paramycoides; carob waste; crotonic acid; polyhydroxybutyrate (PHB); valorization.