Coffee by-products: An underexplored source of prebiotic ingredients

Figures & data

Figure 1. Potential of coffee by-products as prebiotic ingredients.

Table 1. Gut-residing bacteria found associated to the production of SCFA.

Adapted from Tran and Mohajeri (2021).

Table 2. Chemical composition of the different by-products obtained along the coffee chain (values reported in dry weight).

Component	Husk	Pulp	Mucilage	Parchment	Defective beans	Silverskin	Spent coffee grounds
Macronutrients (%)
Lipids	1.50	0.61	–	0.30–4.10	8.10–13.60	1.19–6.30	2.29–24.30
Protein	6.80	8.74–17.37	17.00	3.10–17.40	14.5–17.0	10.90–20.60	11.20–18.8
Ash	1.40–6.20	9.55	–	6.30	4.80–6.0	3.47–10.5	0.50–2.20
Total carbohydrates	–	15.68–63.57	–	–	58.60	5.80–7.97	62.2–69.4
Total sugars	26.50	9.70	–	–	8.00	0.40	–
Glucose	–	–	–	–	–	23.77	12.40
Fructose	–	–	–	–	–	–	–
Mannose	–	–	–	–	–	1.77	19.07
Xylose	–	–	–	–	–	7.61	–
Galactose	–	–	–	–	–	3.76	16.43
Arabinose	–	–	–	–	–	3.54	3.60
Total fiber	31.86–43.00	28.00	–	64.3–92.60	56.40	52.00–69.80	47.30–60.46
Insoluble	26.00	10.00	–	92.10	–	44.2–66.00	41.63–56.8
Soluble	17.00	18.00	–	0.50	–	3.40–11.20	0.80–9.68
Cellulose	24.50–35.40	20.7	8.00	6.00–12.00	–	10.33–23.77	12.40
Hemicellulose	28.46–29.17	3.60	18.00	28.00	–	7.7–16.68	39.10
Pectic polysaccharides	–	–	30.00	4,00–7,00	–	–	–
Lignin	22.35–23.70	14.30	–	27.00–32.00	–	28.58–30.50	23.90–25.01
Bioactive compounds (mg/g)
Total phenolics	12.20	10.20	–	2.30	–	3.60–20.30	12.00
Caffeine	6.85–12.0	2.04–10.12	–	1.34	13.4–45.16	0.68–9.50	1.94–7.88
Tannins	93.00	–	–	–	2.46	2.48	–
CGA	–	1.80–3.37	–	0.05	42.60–44.30	2.46	2.12–7.66
5—CQA	0.84	1.72	–	–	–	0.01–3.16	0.40–2.64
Melanoidins	–	–	–	–	–	–	8.77–11.47
HMF	–	–	–	–	–	0.17–3.21	0.06
References	(Baeta et al. 2017; Bekalo and Reinhardt 2010; Brand et al. 2000; Collazo-Bigliardi, Ortega-Toro, and Boix 2018; da Silva et al. 2022; Murthy and Naidu 2012)	(da Silva et al. 2022; Dias et al. 2015; Murthy and Naidu 2012; Patil et al. 2022)	(Avallone et al. 2000)	(Benitez et al. 2021; Benitez et al. 2019; Iriondo-DeHond, García, Fernandez-Gomez, et al. 2019; Littardi et al. 2020; Mirón-Mérida et al. 2019)	(da Silva et al. 2022; Habtamu and Belay 2020; L. S. Oliveira et al. 2006; Prandi et al. 2021; Vasconcelos et al. 2007)	(Ateş and Elmacı 2019; Ballesteros, Teixeira, and Mussatto 2014; Bessada et al. 2018; Costa et al. 2018; da Silva et al. 2022; Hijosa-Valsero et al. 2018; Iriondo-DeHond, García, Fernandez-Gomez, et al. 2019; Niglio et al. 2019; Prandi et al. 2021; Wen et al. 2021)	(Ballesteros, Teixeira, and Mussatto 2014; Castaldo, Lombardi, et al. 2021; Coelho et al. 2021; Cosío-Barrón, Hernández-Arriaga, and Campos-Vega 2020; Cruz et al. 2012; Martinez-Saez et al. 2017; Vazquez-Sanchez et al. 2018)

CGA: chlorogenic acids; CQA: caffeoylquinic acid; HMF: hydroxymethylfurfural.

Table 3. An overview of the prebiotic effect of coffee and their by-products.

Substrate	Experimental design/trial	Microbiota/metabolite analysis	Main outcomes	Reference
In Vitro Assays
MOS—SCG	Cultivation of three probiotic LAB strains and three pathogenic bacterial strains; lGastrointestinal tolerance test using MOS-cultured LAB, under different conditions (PBS, α-amylase, 0.1 M HCl, 0.3% bile extract).	↑ L. acidophilus l↑ L. casei l↑ L. plantarum l↓ B. cereus l↓ E. coli l↓ S. paratyphi	LAB growth stimulation; Pathogen growth inhibition; lLow survival of LAB under bile extract conditions.	(Wongsiridetchai et al. 2021)
MOS—SCG	Gastrointestinal digestion; lCultivation of three probiotic LAB strains and three pathogenic bacterial strains.	↑ L. acidophilus l↑ L. casei l↑ L. plantarum l↓ B. cereus l↓ E. coli l↓ S. paratyphi	Lower MOS-SCG digestibility compared to commercial prebiotics (MOS, FOS and GOS); lLAB growth stimulation; Pathogen growth inhibition. l	(Puengsawada et al. 2021)
OS—SCG	Cultivation of four Lactobacillus strains	↑ L. gasseri l↑ L. reuteri	Hydrolyzed SCG showed to be more effective compared to an established prebiotic such as inulin.	(Sarghini et al. 2021)
OS—SCG (green coffee)	Cultivation of three probiotic LAB strains; lResistance to artificial human gastric juice.	↑ L. fermentum l↑ L. casei l↑ L. plantarum	LAB growth stimulation; lNon-digestibility of SCG close to 90% (pH 1); lLower SCG digestibility compared to inulin.	(Desai et al. 2020)
Galactomannans—SCG	Cultivation of two probiotic strains;	↑ B. adolescentis l↑ L. acidophilus l↑ SCFA: acetate, propionate, and butyrate	Probiotic bacterial growth stimulation;	(J. Gu et al. 2020)
Hydrolyzed SCG	Fecal fermentation with MOS obtained through hydrolysis under various temperature (170-220 °C) and time (10-60 min) conditions	↑ Beneficial genera: Barnesiella, Anaerostipes, Blautia, Clostridium XVIb, Coprococcus, Butyricicoccus, Intestinimonas, Ruminococcus, Odoribacter, Pseudoflavonifractor and Veillonella l↑ Bilophila l↑ SCFA: acetate, propionate, and butyrate	Stimulation of the growth of some beneficial genera; lSCFA production increase in a dose-dependent manner; lHMF and polyphenols could have an inhibitory effect on other beneficial genera.	(Perez-Burillo et al. 2019)
Hydrolyzed SCG	Simulated digestion followed by fecal fermentation; lIncubation of human hepatoma HepG2 cells with HSCG, digested HSCG, fermented HSCG, or residual fraction from fermented HSCG for 20 h.	↑ Bifidobacterium spp. l↑ Lactobacillum spp. l↓ Clostridium spp. l↓ Bacteroides spp. l↑ SCFA: acetate, propionate, and butyrate ↑ antioxidant compounds	Probiotic bacterial growth stimulation; lPathogen growth inhibition; l↑ chemoprotective activity; l↑ antioxidant activity.	(Panzella et al. 2017)
Polyphenolic extract—SCG	Cultivation of several Lactobacilli and Bifibobacteria species; lCultivation of four pathogenic bacterial strains;	↓ B. cereus l↓ S. aureus l↓ S. Typhimurium l↓ E. coli	Probiotic bacterial growth stimulation at a level comparable to the control (probiotic strains grown only in MRS broth); lPathogen growth inhibition.	(Klangpetch 2017)
Melanoidins—SCG	Gastrointestinal digestion followed by fecal fermentation (24 h)	↑ Lactobacillus spp. l↑ Bifidobacterium spp. l↓ S. aureus	Coffee melanoidins at a physiological concentration stimulated the growth of probiotic bacteria.	(Jiménez-Zamora, Pastoriza, and Rufián-Henares 2015)
SCG	Gastrointestinal digestion followed by fecal fermentation (24 h)	↑ SCFA: acetate, propionate, and butyrate	SCG oligosaccharides displayed modest changes during gastric and small intestine phases; lSCG can be fermented by colonic microbiota producing SCFA.	(Cosío-Barrón, Hernández-Arriaga, and Campos-Vega 2020)
SCG without the presence of melanoidins	Gastrointestinal digestion followed by fecal fermentation (24 h); lCultivation of pathogenic bacterial strains.	↑ Lactobacillus spp. l↑ Bifidobacterium spp. l↔ Bacteroides spp. . l↔ Clostridium spp.	Probiotic bacterial growth stimulation; lInsignificant antimicrobial effect against E. coli and S. aureus.	(Jiménez-Zamora, Pastoriza, and Rufián-Henares 2015)
SCG	Gastrointestinal digestion followed by fecal fermentation (24 h).	↑ SCFA: acetate, propionate, and butyrate	SCG can be fermented by colon microbiota producing SCFA.	(Lopez-Barrera et al. 2016)
XOS—silverskin	Fermentation of XOS with L. casei	↑ L. casei l↑ organic acids	pH decrease; lXOS level reduce.	(Ratnadewi et al. 2020)
Silverskin	Gastrointestinal digestion followed by fecal fermentation; lCultivation of pathogenic bacterial strains.	↑ Lactobacillus spp. l↑ Bifidobacterium spp. l↔ Bacteroides spp. l↔ Clostridium spp.	Probiotic bacterial growth stimulation; lInsignificant antimicrobial effect against E. coli and S. aureus.	(Jiménez-Zamora, Pastoriza, and Rufián-Henares 2015)
Silverskin	Fecal fermentation	↑ Bifidobacteria l↓ Bacteroides spp. l↓ Clostridia	Lactobacillus spp. showed a limited aptitude to use CS for their growth; lPathogen growth inhibition.	(Borrelli et al. 2004)
Aqueous extract—coffee pulp	Gastrointestinal digestion; lCultivation of pathogenic and probiotic bacterial strains with coffee pulp extract and digested coffee pulp extract.	↔ L. acidophilus l↓ E. coli l↓ S. aureus	Coffee pulp extract can be a potential natural antimicrobial for food industry with no effect on the probiotics.	(Khochapong et al. 2021)
XOS—coffee husks	In vitro digestibility tests; lCultivation of four probiotic cultures of Lactobacillus and Bifidobacterium.	↑ B. longum l↑ L. acidophilus l↑ L. paracasei	With the exception of B. lactis all the probiotic cultures were able to utilize XOS as carbon source; lFast decrease of the concentrations of xylobiose and xylotriose, after fermentation.	(Ávila, Martins, Costa, et al. 2020)
Medium roasted coffee	Cultivation of four probiotic strains and one pathogenic bacterial strain;	↑ L. rhamnosus l↑ L. acidophilus l↑ B. animalis l↓ E. coli	Probiotic bacterial growth stimulation.	(Sales et al. 2020)
Coffee (rich in CGA)	Fecal fermentation	↑ Bifidobacterium spp. l↑ C. coccoides l↑ E. rectale l↑ Bacteroides spp. l↑ dihydrocaffeic acid l↑ dihydroferulic acid	No change in the growth of Lactobacillus spp. and Enterococcus spp. lRapid metabolism of CGA; lCaffeine remained unmetabolized.	(Mills et al. 2015)
Coffee	Cultivation of two pathogenic bacterial strains;	↓ E. faecalis l↓ E. coli	Pathogen growth inhibition.	(Nakayama and Oishi 2013)
Melanoidins—coffee	Gastrointestinal digestion followed by fecal fermentation	↑ Bifidobacterium spp. l↑ SCFA: acetate, propionate, and butyrate l↑ lactate l↑ phenolic metabolites	Poor fermentation compared to melanoidins from bakery products, however superior to the blank sample (inoculum and buffer only); l51% of coffee melanoidins phenolics were represented by microbial metabolites.	(Perez-Burillo et al. 2020)
Experimental Animal Models
Coffee pulp	Male rats (n = 48), with 8-9 weeks of age, were divided into 4 groups for the 16-week feeding protocol: corn starch; corn starch + coffee pulp (5% in the final 8 weeks); diet high in fat and carbs; diet high in fat and carbs + coffee pulp (12.5% in the final 8 weeks)	↑ Clostridium saudiense l↑ Akkermansia muciniphila l↑ Cronobacter malonaticus l↑ Cronobacter sakazakii	↑ genera involved in the development and treatment of obesity; l↓ body weight and abdominal fat	(Bhandarkar et al. 2021)
Polyphenolic extract—coffee husks	Female mice, with 6-8 weeks of age, were divided into 4 groups (n = 8 mice/group): control group; DSS group; DSS + low-dose extract (10 mg/kg) treatment group; DSS + high-dose extract (30 mg/kg) treatment group. l2.5% DSS (w/v) in the drinking water for 7 days, and extract for 9 days (via intragastric administration).	↑ Bacteroides l↓ Enterococcus l↓ Helicobacter l↓ Allobaculum l↓ Lachnospiraceae	Polyphenolic extract coffee husks restored the gut microbiota modified by DSS; lThese extracts can alleviate brain inflammation.	(Li et al. 2022)
SCG	Male rats (n = 48), with 8-9 weeks of age, were divided into 4 groups for the 16-week feeding protocol: corn starch; corn starch + SCG (5% in the final 8 weeks); diet high in fat and carbs; diet high in fat and carbs + SCG (5% in the final 8 weeks)	↓ Firmicutes/Bacteroidetes ratio l↓ Verrucomicrobia l↓ Erysipelotrichaceae l↓ Clostridium sensu l↑ Lachnospiraceae	SCG increased the diversity of the gut microbiota; l↑ family linked to obesity and protection against colon cancer. l↓ family involved in the establishment of gastrointestinal disease	(Bhandarkar et al. 2020)
Silverskin extract	Male rats (n = 15) and female rats (n = 15), both 3 weeks of age, were divided into two groups: control (7 males and 7 females) and group treated silverskin extract (8 males and 8 females) for 28 days.	↑ SCFA: acetate, propionate, and butyrate	Silverskin extract can be fermented by colon microbiota producing SCFA.	(Iriondo-DeHond, Rios, Herrera, et al. 2019)
Caffeinated coffee	Four-week-old female mice were given daily oral gavage of caffeinated coffee, decaffeinated coffee, or water (n = 12 per group) lAfter 5 days of gavage, half of each group were administered amoxicillin for 7 days. Oral gavage of coffee or water was continued throughout antibiotic treatment.	↓ Proteobacteria l↓ Burkholderiaceae l↑ Akkermansiaceae	↓ abundance of potentially pro-inflammatory bacteria	(Diamond et al. 2021)
Coffee	Male rats (n = 32) were adaptively fed for 1 week; After 1 week, rats were divided into 4 groups: control; PSD model group; PSD + conventional coffee group; PSD + decaffeinated coffee group. Each day of PSD processing (7 days), coffee and pure water were administered.	↑ Akkermansia l↓ Lachnospiraceae l↓ Oscillospira	Coffee and decaffeinated coffee can restore the gut microbiota affected by PSD.	(X. Gu et al. 2022)
Coffee	Male rats (n = 28) were divided into 4 groups for the 56-day feeding protocol: control diet group; high fat diet group; coffee + control diet group; coffee + high fat diet group.	↑ Bifidobacterium spp. l↓ E. coli l↔ Enterococcus spp.	Coffee exhibits positive health effects in rats with obesity-induced; l↑ serum high-density lipoprotein cholesterol	(Cavalcanti et al. 2022)
Coffee	Seven female mice, with 8 weeks of age, were acclimatized for 1 week to the standard laboratory conditions; lAfter 1 week, each of the seven mice consumed either coffee, GOS or sterile water at the same time of day for 3 consecutive days.	↑ Bifidobacterium spp. l↓ E. coli l↓ Clostridium spp. l↑ aquaporin8	Coffee intake can regulate gut microbiota and maintain intestinal balance; l↑ cramp expression	(Nakayama and Oishi 2013)
Coffee	Male rats (n = 40) were randomized to chow (12% kcal fat) or high-fat (60% kcal fat) diet. lEach group was further divided into water or caffeinated coffee for 10 weeks.	↑ SCFA (acetate, formate, and propionate) l↓ BCAA l↓ Firmicutes/Bacteroidetes ratio l↓ Clostridium Cluster XI	↓ body weight, liver triglycerides, adiposity, and energy intake l↓ insulin sensitivity lCoffee consumption can alter gut microbiota in high-fat-fed rats	(Cowan et al. 2014)
Human Trial
Coffee	Healthy adult volunteers (n = 16), aged between 21 and 57 years, consumed a daily dose of 3 cups of coffee for 3 weeks.	↑ Bifidobacterium spp. l↑ Lachnospira l↑ Roseburia l↔ Prevotella	Little impact on the dominant bacterial groups; lIncrease in the metabolic activity.	(Jaquet et al. 2009)

MOS: mannanoligosaccharides, SCG: spent coffee grounds, PBS: phosphate buffer saline, OS: oligosaccharides; SCFA: short-chain fatty acids, DSS: dextran sodium sulfate, PSD: paradoxical sleep deprivation, BCAA: branched-chain amino acids. The arrows represent the change in the microbial population/metabolite production: ↑ increase, ↓ decrease, ↔ no change.

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