Okara, a soybean by-product from soymilk and tofu production, is generated in large amounts,
with approximately 1.1–1.2 kg of wet okara produced per kg of soybean processed. For example,
Frias Nutrición (Burgos) produces 7700 tons annually, contributing to approximately 14 million
tons worldwide. Due to its high moisture content, storage is costly, requiring drying to prevent
spoilage. Discarding it would a significant loss of valuable proteins and fiber. Valorizing okara,
especially by recovering proteins and sugars from fiber, without drying pretreatment, would
significantly reduce costs and enhance sustainability. The first step to valorize okara was protein
hydrolysis using reduced-pressure alkaline pretreatment (RPAP), varying pressure, time, and
NaOH concentration. Two optimal conditions were identified at 70 °C using 5 % okara (w/v): (A)
455 mbar, 180 mM NaOH for 1 h (77 ± 3 % yield), and (B) 300 mbar, 100 mM NaOH for 2 h
(75 ± 1 % yield). Techno-economic assessment identified process B as more efficient and
sustainable at industrial scale. Residual solids from both extractions were subsequently subjected
to enzymatic hydrolysis with Cellic® CTec2 (40 FPU/g biomass at 5 % and 10 %), releasing a
high content of simple sugars. These hydrolysates were used for lactic acid fermentation with
Ligilactobacillus salivarius ATCC 11742 to assess their suitability as substrates. Each hydrolysate
was tested alone, supplemented with salts and nitrogen sources typical of MRS medium, and
compared to MRS itself. The supplemented hydrolysates showed nearly identical performance to
the ideal medium, confirming their suitability for fermentation without inhibitory effects.
