Development of a Solid-State Fermentation System for Producing Bioethanol from Food Waste

A low-energy paradigm was adopted for sustainable, affordable, and effective urban waste valorization. Here a new, eco-designed, solid-state fermentation process is presented to obtain some useful bio-products by recycling of different wastes. Urban food waste and scraps from trimmings were used as a substrate for the production of citric acid (CA) by solid state fermentation of Aspergillus niger NRRL 334, with a yield of 20.50 mg of CA per gram of substrate. The acid solution was used to extract metals from waste printed circuit boards (WPCBs), one of the most common electronic waste. The leaching activity of the biological solution is comparable to a commercial CA one. Sn and Fe were the most leached metals (404.09 and 67.99 mg/L, respectively), followed by Ni and Zn (4.55 and 1.92 mg/L) without any pre-treatments as usually performed. Commercial CA extracted Fe more efficiently than the organic one (123.46 vs. 67.99 mg/L); vice versa, biological organic CA recovered Ni better than commercial CA (4.55 vs. 1.54 mg/L). This is the first approach that allows the extraction of metals from WPCBs through CA produced by A. niger directly grown on waste material without any sugar supplement. This “green” process could be an alternative for the recovery of valuable metals such as Fe, Pb, and Ni from electronic waste.

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Correlation of brightening with cumulative enzyme activity related to lignin biodegradation during biobleaching of kraft pulp by white rot fungi in the solid-state fermentation system.

Applied and Environmental Microbiology ◽

10.1128/aem.61.2.617-622.1995 ◽

1995 ◽

Vol 61 (2) ◽

pp. 617-622 ◽

Cited By ~ 58

Author(s):

N Katagiri ◽

Y Tsutsumi ◽

T Nishida

Keyword(s):

Enzyme Activity ◽

Solid State ◽

Solid State Fermentation ◽

Kraft Pulp ◽

White Rot Fungi ◽

White Rot ◽

Lignin Biodegradation ◽

Fermentation System

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Solid State Fermentation of Brewers’ Spent Grains for Improved Nutritional Profile Using Bacillus subtilis WX-17

Fermentation ◽

10.3390/fermentation5030052 ◽

2019 ◽

Vol 5 (3) ◽

pp. 52 ◽

Cited By ~ 10

Author(s):

Yong Xing Tan ◽

Wai Kit Mok ◽

Jaslyn Lee ◽

Jaejung Kim ◽

Wei Ning Chen

Keyword(s):

Bacillus Subtilis ◽

Amino Acid ◽

Solid State ◽

Food Waste ◽

Solid State Fermentation ◽

Metabolic Flux ◽

Tricarboxylic Acid Cycle ◽

Fold Increase ◽

Spent Grains ◽

Significant Difference

Brewers’ spent grains (BSG) are underutilized food waste materials produced in large quantities from the brewing industry. In this study, solid state fermentation of BSG using Bacillus subtilis WX-17 was carried out to improve the nutritional value of BSG. Fermenting BSG with the strain WX-17, isolated from commercial natto, significantly enhanced the nutritional content in BSG compared to unfermented BSG, as determined by the marked difference in the level of metabolites. In total, 35 metabolites showed significant difference, which could be categorized into amino acids, fatty acids, carbohydrates, and tricarboxylic acid cycle intermediates. Pathway analysis revealed that glycolysis was upregulated, as indicated by the drop in the level of carbohydrate compounds. This shifted the metabolic flux particularly towards the amino acid pathway, leading to a 2-fold increase in the total amount of amino acid from 0.859 ± 0.05 to 1.894 ± 0.1 mg per g of BSG after fermentation. Also, the total amount of unsaturated fatty acid increased by 1.7 times and the total antioxidant quantity remarkably increased by 5.8 times after fermentation. This study demonstrates that novel fermentation processes can value-add food by-products, and valorized food waste could potentially be used for food-related applications. In addition, the study revealed the metabolic changes and mechanisms behind the microbial solid state fermentation of BSG.

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