Genotypic Characterization of Rhizopus species from Tempeh and Usar: Traditional Inoculum of Tempeh in Indonesia

Abstract

Soybeans tempeh (tempeh) is processed by fermentation using Rhizopus spp. Tempeh is an important source of protein in Indonesia. The traditional inoculum in tempeh fermentation locally is known as Usar, which is made from the leaves of Hibiscus tiliaceus . However, Rhizopus information from Usar is still limited. Therefore, this study aims to identify and investigate the genetic diversity of Rhizopus species from Usar and tempeh based on the Internal Transcribed Spacer (ITS) sequences and the Random Amplified Polymorphic DNA (RAPD) markers. Twenty-three Rhizopus strains were isolated from Usar and ten Rhizopus strains were isolated from tempeh. Based on ITS sequences, the isolates were similar to Rhizopus microsporus (30 isolates) and Rhizopus delemar (3 isolates) with 98-99% similarity. The genetics of R. microsporus and R. delemar are varied and different from the genetics of R. microsporus from tempeh. The growth temperature of R. microsporus varies from 33°C to 48°C and R. delemar can grow to a maximum at 33°C. This research needs to be continued to obtain information about the role of Rhizopus from this study in determining the quality of tempeh.