Optimization of Inulin Hydrolysis by Penicillium lanosocoeruleum Inulinases and Efficient Conversion Into Polyhydroxyalkanoates

• Published in: Frontiers in bioengineering and biotechnology Vol. 9; p. 616908
• Main Authors: Corrado, Iolanda, Cascelli, Nicoletta, Ntasi, Georgia, Birolo, Leila, Sannia, Giovanni, Pezzella, Cinzia
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 01-03-2021
• Subjects: Bioengineering and Biotechnology; biorefinery; inulin; inulin hydrolysis; polyhydroxybutyrate; response surface methodology; simultaneous saccharification and fermentation; biorefinery; inulin; simultaneous saccharification and fermentation; polyhydroxybutyrate; response surface methodology; inulin hydrolysis
• ISSN: 2296-4185; 2296-4185
• DOI: 10.3389/fbioe.2021.616908

Inulin, a polydisperse fructan found as a common storage polysaccharide in the roots of several plants, represents a renewable non-food biomass resource for the synthesis of bio-based products. Exploitation of inulin-containing feedstocks requires the integration of different processes, including inulinase production, saccharification of inulin, and microbial fermentation for the conversion of released sugars into added-value products. In this work paper, a new microbial source of inulinase,
, was identified through the screening of a fungal library. Inulinase production using inulin as C-source was optimized, reaching up to 28 U mL
at the 4th day of growth. The fungal inulinase mixture (
) was characterized for pH and temperature stability and activity profile, and its isoenzymes composition was investigated by proteomic strategies. Statistical optimization of inulin hydrolysis was performed using a central composite rotatable design (CCRD), by analyzing the effect of four factors. In the optimized conditions (T, 45.5°C; pH, 5.1; substrate concentration, 60 g L
; enzyme loading, 50 U g
), up to 96% inulin is converted in fructose within 20 h. The integration of
in a process for polyhydroxyalkanoate (PHA) production by
from inulin was tested in both separated hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). A maximum of 3.2 g L
of PHB accumulation, corresponding to 82% polymer content, was achieved in the SSF. The proved efficiency in inulin hydrolysis and its effective integration into a SSF process pave the way to a profitable exploitation of the
enzymatic mixture in inulin-based biorefineries.