Current evidence most strongly supports fungal cultivation on SCG-containing substrates, bacterial treatment of caffeine-rich wastewaters, yeast fermentation of hydrolyzed residues, and microalgal use of conditioned liquid streams, and microalgal use of conditioned liquid streams.
Abstract
The growing volume of agro-industrial and food-processing residues has intensified interest in their use as low-cost substrates for microbial bioprocessing. Coffee-derived waste streams, including spent coffee grounds (SCGs), wastewater, pulp, husk, and silverskin, represent abundant but still underutilized biomass resources. This narrative review evaluates their potential as liquid or solid substrates or as components of cultivation media for selected microbial systems, including microalgae, bioremediation- and bioprocess-related bacteria, edible fungi such as Pleurotus spp., and yeasts in the genera Pichia, Kluyveromyces, Saccharomyces, and Yarrowia. The review compares the suitability of individual coffee residues based on substrate composition, pretreatment requirements, inhibitory compounds, process limitations, and reported outputs. Coffee-derived residues can reduce substrate costs, support waste valorization, and partially replace conventional nutrients in microbial processes. However, their broader application is limited by compositional variability, conditioning or hydrolysis requirements, difficulties in process standardization, and downstream processing costs. Current evidence most strongly supports fungal cultivation on SCG-containing substrates, bacterial treatment of caffeine-rich wastewaters, yeast fermentation of hydrolyzed residues, and microalgal use of conditioned liquid streams. The review identifies key research gaps and outlines realistic directions for developing coffee-based microbial bioprocesses within a circular bioeconomy framework.
The increasing demand for sustainable bioplastics is constrained by the high production costs associated with refined carbon sources, highlighting the need for low-cost, renewable feedstocks. This study evaluated the potential of spent coffee grounds (SCG), an abundant and sustainable feedstock for generating polyhydroxyalkanoates (PHA) using Cupriavidus necator. First, SCG was subjected to solvent extraction to remove coffee oil, followed by extraction of phenolic compounds, and the remaining biomass was referred to as SCGO. The originality of this work lies in the systematic comparison of acid, alkaline, and peracetic acid pretreatments and their subsequent evaluation for microbial PHA production. SCGO was subjected to various chemical pretreatments, including acid (H2SO4), alkaline (NaOH), and peracetic acid (PAA) pretreatment. The effects of the different pretreatments on SCGO delignification, hydrolysis yield, and enzymatic saccharification to release monomeric sugars were evaluated. Among the tested methods, alkaline pretreatment provided the highest delignification efficiency, enzymatic saccharification, and fermentable sugar recovery, resulting in superior bacterial growth and PHA production. Under optimized conditions, the alkaline-pretreated SCGO hydrolysate supplemented with corn steep liquor produced a maximum biomass concentration of 6.5 ± 0.26 g/L, 60.0 ± 1.45% PHA accumulation, and a PHA titer of 3.89 ± 0.14 g/L. Structural and thermal characterization confirmed that the produced polymer possessed properties comparable to those of conventional poly(3-hydroxybutyrate) (PHB). Overall, this study demonstrates that integrated valorization of spent coffee grounds can effectively generate fermentable substrates for microbial PHA production, providing a sustainable approach for converting agro-industrial residues into high-value bioplastics while supporting circular bioeconomy strategies.
G. Saratale, R. Saratale, R. Bharagava et al.· Polymers· 0 citations
Fermentation remains one of the oldest and most effective biotechnological processes for improving food quality, safety, and shelf life. In Africa, the fermentation of seed-based substrates such as African locust bean (
Parkia biglobosa
), soybean (
Glycine max
), melon seed (
Citrullus lanatus
), Bambara groundnut (
Vigna subterranea
), and sesame (
Sesamum indicum
) plays a vital role in the production of traditional condiments, such as
iru
,
dawadawa
,
ogiri
,
ugba
, and
okpehe.
This review examines the application of functional microorganisms in the fermentation of seed-based substrates and their contributions to the enhancement of nutritional and bioactive properties of fermented food condiments. Functional microorganisms, including lactic acid bacteria,
Bacillus
species, yeasts, and selected fungi, facilitate complex biochemical transformations through enzymatic degradation of proteins, carbohydrates, and lipids. These activities improve nutrient bioavailability, protein digestibility, flavor development, and overall product quality. An ideal functional starter culture must possess several criteria that include safety status, enzymatic capability, acid tolerance, fermentation efficiency, and bioactive metabolite production, are discussed. The review highlights the mechanisms through which microbial fermentation promotes the production of bioactive compounds such as bioactive peptides, bacteriocins, short-chain fatty acids, gamma-aminobutyric acids, and antioxidant metabolites, many of which are associated with antihypertensive, antimicrobial, antioxidant, and gut-health-promoting effects. In addition, fermentation significantly reduces antinutritional factors such as phytates, tannins, oxalates, and trypsin inhibitors, thus enhancing mineral absorption and nutritional utilization. Overall, the integration of functional microorganisms into seed-based fermentation systems offers a sustainable approach to improving the nutritional value, safety, functionality, and commercial potential of traditional fermented condiments. This approach supports food security, promotes the valorization of indigenous seed resources, and contributes to the development of innovative functional foods aligned with modern nutritional and public health needs.
Mercy Okuku, T. Ogunnusi, A. Ojo et al.· F1000Research· 0 citations
Cyanobacteria are increasingly presented as resource-efficient sources of protein, pigments and functional ingredients and as biological inputs that may improve crop production. This critical narrative review evaluates how far those claims are supported for sustainable food production, with emphasis on cultivated edible cyanobacteria, especially commercial Spirulina produced from Limnospira (Arthrospira) platensis, and on selected Nostoc foods. Peer-reviewed literature published from 1 January 2000 to 30 May 2026 was located through PubMed/MEDLINE, the Directory of Open Access Journals, ScienceOpen, FAO AGRIS and OpenAIRE Explore, supplemented by citation searching and verification of article and DOI records. Evidence was appraised for taxonomic precision, compositional representativeness, experimental scale, analytical validity, external validity and the transparency of life-cycle and techno-economic assumptions. Cyanobacterial biomass can supply concentrated protein, minerals, fatty acids and bioactive compounds, while phycocyanin has a distinctive role as a natural blue colourant. However, composition and digestibility vary by strain, cultivation conditions and processing, and many nutritional and food-function claims remain based on in vitro assays or laboratory prototypes. Low inclusion levels can improve the nutritional or technological properties of pasta, bakery and other foods, but colour, odour and flavour often limit acceptance at higher doses. Sustainability is not intrinsic to cyanobacterial production: mixing, temperature control, harvesting and drying can dominate energy demand and cost, and favourable outcomes depend on climate, scale, product form, co-product recovery and credible use of safe circular inputs. Market surveillance also demonstrates the need for source authentication and batch testing for cyanotoxins, metals, microorganisms, composition and allergens. Agricultural biostimulant and biofertiliser pathways are promising but still require stronger field-scale and economic validation. The review concludes that cyanobacteria can contribute to sustainable food systems when strain selection, food-grade process control, low-energy downstream operations, fit-for-purpose product design and transparent environmental accounting are integrated rather than treated as separate optimisation problems.
Deepu Vijayan, S. Biswas, Pratibha Gupta· Asian Journal of Biology· 0 citations
