Integration of Solid State and Submerged Fermentations for the Valorization of Organic Municipal Solid Waste.

Gheorghe-Adrian Martău,Joachim Venus,José Pablo López-Gómez,Roland Schneider,Peter Unger,Dan Cristian Vodnar

doi:10.3390/jof7090766

Abstract

Solid state fermentation (SsF) is recognized as a suitable process for the production of enzymes using organic residues as substrates. However, only a few studies have integrated an evaluation of the feasibility of applying enzymes produced by SsF into subsequent hydrolyses followed by the production of target compounds, e.g., lactic acid (LA), through submerged-liquid fermentations (SmF). In this study, wheat bran (WB) was used as the substrate for the production of enzymes via SsF by Aspergillus awamori DSM No. 63272. Following optimization, cellulase and glucoamylase activities were 73.63 ± 5.47 FPU/gds and 107.10 ± 2.63 U/gdb after 7 days and 5 days of fermentation, respectively. Enzymes were then used for the hydrolysis of the organic fraction of municipal solid waste (OFMSW). During hydrolysis, glucose increased considerably with a final value of 19.77 ± 1.56 g/L. Subsequently, hydrolysates were fermented in SmF by Bacillus coagulans A166 increasing the LA concentration by 15.59 g/L. The data reported in this study provides an example of how SsF and SmF technologies can be combined for the valorization of WB and OFMSW.

Highlights

Published: 16 September 2021The massive generation of solid waste has made their disposal an important challenge to overcome
This was achieved by (1) using a fungus specialized in enzyme production (Aspergillus awamori) via Solid state fermentation (SsF) and wheat bran (WB) as a substrate; (2) the fermented substrate rich in enzymes obtained was used in the hydrolysis of OFMSW to increase sugars; (3) sugars rich hydrolysates were used as the substrate in submerged-liquid fermentations (SmF) by a Bacillus specialized in L–lactic acid production
In our experiments, WB and WB supplemented with glucose (WB+G) were evaluated as substrates for SsF with A. awamori to produce enzymes with potential application in enzymatic hydrolyses

Summary

Introduction

The massive generation of solid waste has made their disposal an important challenge to overcome. Global municipal solid waste (MSW) production is expected to increase up to. 70% by 2050 from 2010 million tons (Mt) in 2016 [1]. In addition to MSW, substantial global industrialization has contributed to an unprecedented increase in the generation of industrial solid waste. In 2017, the rate of industrial waste generation was approximately. 18 times higher than MSW [2]. A large portion of industrial wastes and MSW are organic residues, which can be used as substrates in fermentations. The organic fraction of municipal solid wastes (OFMSW) represents an ample category of bio-waste

Methods

Results

Conclusion