Bioconversion and Valorization of Moroccan Prunus dulcis Cultivars: Upcycling Plant Biomass into Functional Probiotic Bio-Matrices via Symbiotic Fermentation

The transition toward a circular bioeconomy requires advanced bioprocessing strategies to upgrade agricultural biomass into high-value functional ingredients. This study evaluates the biological upcycling of plant-based matrices derived from three indigenous Moroccan cultivars of Prunus dulcis (Assoul, Aknoul, and Al Hoceima) via symbiotic kefir fermentation. Raw kernels were subjected to aqueous extraction at a standardized 1:9 w/v ratio, generating an extractable liquid phase targeted for microbially driven functional enrichment. The matrices were pasteurized and fermented with a symbiotic kefir culture at 25°C for 24 hours, followed by a 21-day storage assessment to monitor bioconversion stability.

Fermentation triggered significant biochemical alterations across all varietal substrates; pH consistently decreased to a stable range of 4.7–5.2, while titratable acidity increased to 1.7–2.1% by Day 21. Total soluble solids drastically declined to final contents of 0.580–0.590%, confirming intensive microbial utilization of the fermentable carbohydrate fractions. From a resource valorization perspective, the bioprocess acted as a potent functional multiplier. Total phenolic content experienced a 2-to-3-fold inflation, peaking at 0.95 mg GAE/mL in the Al Hoceima matrix by Day 7. This enzymatic release of bound phenolics directly correlated with antioxidant amplification, as DPPH radical scavenging capacity more than doubled to reach optimal peaks of 62.0–66.1%.

At the terminal stage, the bio-upcycled matrices maintained dense, viable probiotic consortia, with lactic acid bacteria populations reaching 8.27–8.33 log CFU/mL, thus exceeding established therapeutic efficacy thresholds. Principal Component Analysis verified that baseline compositional variance across cultivars dictates fermentation kinetics and functional output, with the Al Hoceima variety demonstrating superior bioconversion efficiency and organoleptic quality. Ultimately, this research provides a technical framework for the clean biological transformation of regional crop assets, validating fermentation as a sustainable pathway to generate premium functional inputs from native plant biomass.