Evaluation of a process for producing fermentable sugars from porva corn by Rhizopus oryzae

Abstract

This work aimed to assess the effectiveness of utilizing Rhizopus oryzae for starch hydrolysis from Porva corn (Zea mays) by evaluating different conditions during the fungus growth process in solid-state fermentation and enzymatic hydrolysis. The goal is to propose a potential methodology to produce commodities like beer, bypassing the traditional grain malting phase. Solid-state fermentation (SSF) was employed to analyze fungal growth on cereal cooked at distinct time intervals (0 min, 30 min, and 60 min) over 72 hours, maintaining an incubation temperature of 32 ºC. Subsequent enzymatic hydrolysis, conducted in the liquid phase at different temperatures (32 ºC, 44 ºC, and 56 ºC) for 5 hours, aimed to extract maximum fermentable sugars. Parameters such as cell concentration, reducing sugars, and dissolved solids (ºBrix) were measured. Furthermore, solid samples obtained at each stage underwent Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy analysis to identify changes in the composition of maize that occurred in each phase. The results indicate that the growth phase exhibited a significantly higher cell concentration of R. oryzae when corn was subjected to a 60-minute cooking pre-treatment. Conversely, the most favorable conditions for glucose concentration were observed during the hydrolysis phase at a temperature of 56 ºC, reaching up to 307 mg_glucose/g_corn (51.23% of hydrolyzed starch). Subsequently, the obtained hydrolysate underwent fermentation for 84 hours using commercial yeast (Saccharomyces cerevisiae), resulting in a corn-based ferment with an alcohol content of 12% ABV, demonstrating that the process has good application potential in the manufacture of alcoholic beverages.

Keywords:
Solid state fermentation; Enzymatic hydrolysis; Porva corn; Rhizopus oryzae

HIGHLIGHTS

Rhizopus oryzae augmented starch hydrolysis when employing 60-minute cooked Porva corn

Enzymatic hydrolysis of corn koji at 56 °C yielded high starch breakdown (51.23%)

Corn-koji hydrolysates produced 12% alcohol, suitable for cereal malting enhancement