Abstract
Yeast can be isolated from tofu wastewater and the cell wall in the form of β-glucan can act as a natural decontaminant agent. This study aimed to isolate and characterize native yeast from tofu wastewater, which can be extracted to obtain β-glucan and then identify the yeast and its β-glucan activity regarding antifungal ability against Aspergillus flavus and aflatoxin-reducing activity towards aflatoxin B1 (AFB1) and B2 (AFB2). Tofu wastewater native yeast was molecularly identified, and the growth observed based on optical density for 96 h and the pH also measured. β-glucan was extracted from native yeast cell walls with the acid-base method and then the inhibition activity towards A. flavus was tested using the well diffusion method and microscopic observation. AFB1 and AFB2 reduction were identified using HPLC LC-MS/MS. The results showed that the native yeast isolated was Pichia norvegensis with a β-glucan yield of 6.59%. Pichia norvegensis and its β-glucan showed an inhibition zone against Aspergillus flavus of 11.33 ± 4.93 and 7.33 ± 3.51 mm, respectively. Total aflatoxin-reducing activity was also shown by Pichia norvegensis of 26.85 ± 2.87%, and β-glucan of 27.30 ± 1.49%, while AFB1- and AFB2-reducing activity by Pichia norvegensis was 36.97 ± 3.07% and 27.13 ± 1.69%, and β-glucan was 27.13 ± 1.69% and 32.59 ± 4.20%, respectively.
Highlights
Tofu wastewater from the tofu industry is generated in large amounts; if it is not utilized and thrown away, it will have a bad impact on the environment
Tofu wastewater is a source of a potential native yeast that has antifungal and toxinreducing activity, especially towards A. flavus and aflatoxin
As native yeast isolated from tofu wastewater, showed promising antifungal and toxin-reducing activity towards A. flavus and aflatoxin
Summary
Tofu wastewater from the tofu industry is generated in large amounts; if it is not utilized and thrown away, it will have a bad impact on the environment. The largest component of tofu wastewater is protein (N-total) of 226.06 to 434.78 mg/L, while the gases found in tofu wastewater disposal are nitrogen gas (N2), oxygen (O2), hydrogen sulfide (H2S), ammonia (NH3), carbon dioxide (CO2), and methane (CH4) [2]. These gases come from the decomposition of organic materials contained in the wastewater and in general the hydrogen ion concentration of the tofu wastewater tends to be acidic. One way to reduce these problems is to utilize tofu wastewater
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