Optimising amino acid production and recovery through consolidated bioprocessing utilising pineapple plant stem as a substrate

The surge in global pineapple production has resulted in a significant excess of waste, requiring a sustainable bioconversion approach. Despite the substantial volume, pineapple plant stems (PPS) are often neglected and discarded as on-farm waste. Inadequate disposal practices like dumping and open burning pose environmental risks. This study addresses critical gaps in amino acid production from agricultural biomass, emphasising a sustainable approach. The objectives of the research are to enhance glucose recovery from PPS through an enzymatic hydrolysis approach, specifically focusing on amino acids production using separate enzymatic hydrolysis and fermentation (SHF). Additionally, the study explores a consolidated bioprocessing (CBP) approach for amino acid production from PPS and aims to optimise the process using response surface methodology (RSM). Furthermore, the research investigates the recovery of amino acids from fermentation broth, employing ion-exchange solid-phase extraction (SPE). This study employs a systematic approach to explore the potential of PPS for amino acid production. It begins with analysing PPS gelatinisation properties and evaluating its functional characteristics. Enzymatic hydrolysis of PPS generates fermentable sugars, facilitating screening for amino acid-producing bacteria by Pediococcus acidilactici Kp10, P. acidilactici ATCC 8042, and Bacillus subtilis ATCC 6051. The selected strains undergo secondary screening for suitability in amino acid production. Experimental design involves a two-level fractional factorial design and central composite design for parameter optimisation. Amino acid production from PPS was conducted under optimised conditions. Recovery of amino acids from PPS was studied using SPE, considering factors like pH, sample loading volume, and eluent volume, followed by characterisation of recovered amino acids by HPLC. Results indicated that a gelatinisation temperature of 100°C for 15 min achieved the maximum glucose recovery, demonstrating a 3.53-fold increment over the control. Subsequently, the fermentable sugar obtained from PPS hydrolysate was utilised for amino acids production by the selected amino acid producer, B. subtilis ATCC 6051. The study revealed that B. subtilis ATCC 6051 successfully produced 23.53 g/L of amino acids with a productivity of 0.49 g/L/h through SHF. When applying CBP utilising PPS as substrate, B. subtilis ATCC 6051 demonstrated significant amino acid production, yielding 1.28 g/L of total free amino acids, representing a 13% increase in concentration and a 12% boost in yield compared to commercial starch. The study emphasised the pivotal role of medium composition, highlighting the significance of PPS as substrate. Notably, the study achieved a substantial improvement in total amino acids production under optimised CBP condition, reaching 9.57 g/L with a yield of 423.97 mg/g and a remarkable 6.32-fold increment. Furthermore, optimised weak anion SPE effectively recovered amino acids, achieving the highest yield of 5.30 g/L. As conclusion, this study addressed the environmental impact by exploring the sugar recovery potential of PPS, particularly its starch content for amino acid production. This study also explores a promising alternative involving a single-step approach, utilising microorganisms to combine enzymatic hydrolysis and fermentation processes for amino acid production from PPS through CBP approach, followed by its recovery using SPE.

Text 125035 fulltext.pdf Download (1MB) Official URL or Download Paper: https://ethesis.upm.edu.my/id/eprint/18797

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