Table 1.

Some top challenges to which microbial enzymes can contribute towards a sustainable bioeconomy in the next decade

Biological process	Technical challenges/solutions and innovations needed	Highly accessed reviews and spotlight paper in the field
Decarbonization: capturing CO2	Developing efficient in vivo and in vitro processes using microbial CO2 fixing enzymes	Appel et al. (2013), Lemaire et al. (2020), Erb and Zarzycki (2016)
Decarbonization: oxidizing CH4	Developing efficient in vivo and in vitro processes using methane oxidizing enzymes	Sirajuddin and Rosenzweig (2015), Lawton and Rosenzweig (2016), Clomburg et al. (2017)
Plastics removal from the environment and establishing recycling concepts for circular use	Identifying enzymes acting on polymers, such as PE, PVC, PS, PA and PU; upscaling and optimizing processes for PET and ester-based PU but also epoxy-based polymers	Danso et al. (2019), Wei and Zimmermann (2017), Urbanek et al. (2018)
Generating high quality and large amounts of versatile bioplastics	Reducing costs for production, increasing production scale; defining better natural polymers with better properties in designer bugs; optimize harvesting from cells	Di Bartolo et al. (2021), Choe et al. (2021), Zhao et al. (2020), Raza et al. (2018)
Providing truly renewable liquid and gaseous fuels from 2nd and 3rd generation	Hydrolysis of complex lignolytic plant material, better performing (engineered) microbial communities or single organisms. Obtain better genetic tools to manipulate and engineer alga and to improve 3rd generation biofuel production; improved tools to engineer bacteria/archaea involved in biogas and bioalcohol production	Lynd (2017), Callegari et al. (2020), Shuba & Kifle (2018), Milano et al. (2016), Keasling et al. (2021)
Providing sustainable nontoxic biocides or probiotic microbes for plant and animal protection	Establishing efficient synthesis routes using novel enzymatic activities; solvent tolerance Identifying probiotic communities or single organisms	Yi et al. (2021a, b), Lee et al. (2012), Bell et al. (2021)
Identifying novel biocatalytic reactions for synthesis of fine and bulk chemicals	Identify more and better enzymes forming amide and C–C bonds; enzymes acting on ether bonds; increase available transferases, halogenases and others Better host strains, explore the dark matter proteins with no assigned function	Rosano and Ceccarelli (2014), Hauer (2020), Intasian et al. (2021)
Digitalization and tool development for faster engineering, enzyme delivery advancing ultrahigh throughput enzyme mining approaches	Investing in and developing enzyme technology driven platforms, developing machine learning and automatization	Damborsky and Brezovsky (2014), Qu et al. (2019) Mazurenko et al. (2020), Dörr et al. (2016), Markel et al. (2020), Colin et al. (2015)