Biosurfactants (BSs) are surface-active agents (surfactants) produced by microorganisms. In a broad sense, it is understood as surfactants produced by whole living organisms, but most of the surfactants used as BS in the world are fermented products. In recent years, global leading companies have entered the industrial field, increasing competition in the BS business. Additionally, there has been active BS research in the academic field. A group of researchers, mainly from Europe, have held the Biosurfactant International Conference since 2019 and recently opened Research Topics in Frontiers in Bioengineering and Biotechnology, where 15 papers have been published. In this article, we will outline the situation surrounding BSs and then introduce several selected topics.

Mannosylerythritol lipid (MEL), a biosurfactant produced by basidiomycetous yeast, is a sustainable material that is highly biodegradable and safe. MEL has excellent surface-active properties and self-assembly abilities. In addition, its application as a cosmetic ingredient has been pioneering, taking advantage of its characteristic bioactive action. Meanwhile, research and development efforts are underway to expand into other markets. For example, in the agricultural field, MEL shows promise as an agricultural spreading agent, enhancing the effectiveness of agrochemicals while reducing environmental impacts. In the livestock industry, the selective antimicrobial properties of MEL are being explored for use as a feed additive to inhibit methanogenesis in ruminants and as an antibiotic-free mastitis ameliorant. Furthermore, applications of MEL are expected to expand to the field of daily life materials, where it is expected to provide moisture retention, antiviral effects, and film surface conditioning effects. This paper provides an overview of the potential applications of MEL, a next-generation biobased material that is gaining attention, in these diverse fields.

Waste frying oil (WFO) is a degraded oil from repeated exposure to high temperatures during cooking. Many research studies about recycling WFO are highly promoted to reduce its negative impact on the environment, with one of them focused on the production of a naturally-derived eco-friendly biosurfactant, sophorolipid (SL). SL has many advantages for the environment and people, but its production cost is high. Using WFO as a SL substrate for production may lead to cost reduction as it is less expensive than fresh oil. However, its physical characteristics are different from fresh oil and its effect on SL productivity (g/day) has not been investigated. This research focused on the effect of acid value (AV), peroxide value (PV) and carbonyl value (CV) of WFO on SL productivity. It was confirmed that the produced SL concentrations of 106.7~113.0g/L for six kinds of WFOs did not differ significantly from that of 111.1g/L for fresh oil with CV< 0.01. However, WFO required longer culture period (9 days) to reach the same SL concentration when higher degradation oil was used, compared to that of fresh oil (6 days).