The Koji Fermenteria Home Page

Logo with circle

Authentic Japanese koji making


  Welcome to The Koji Fermenteria’s website and wonderful world of koji!

 We are London-based small fermenterium specialised in traditional koji making. We make koji in small batch using Japanese koji-buta method (like picture shown above) which enable us to closely monitor its growth.

 Lately koji is treated as a rising star among chefs and fermentation enthusiasts all over the world and various new innovative koji making methods are starting to emerge. Although every idea has its own merit and of course there is no right or wrong answer, we feel someone needs to strictly follow the tradition based on the understanding of how and why it has been developed. We would like to take this role and contribute to the further development of newly born global koji culture.

 Let me introduce a little bit about koji. Koji is an intrinsic microbe which has been co-habited with Japanese for millenniums and, without doubt, contributed to the development of umami-based Japanese food culture (it indeed has done numerous amounts of miraculous works on it. Click here for more detail about koji).

 Whereas koji is strongly associated with Japanese food, the principle of it can be applied to any types of cuisine. We believe koji can offer huge potential to open a new dimension to already accomplished many locale cuisines in the world. This is what we want to see and is our motivation to roll out our various activities.

Close-up picture of koji
Koji grown in koji-buta
Traditionally made koji
Newly born koji baby

Meet Haruko

 Haruko learnt koji making from Nakaji, the author of the highly praised “Koji for Life” and is a certified koji specialist (accredited by Nakaji’s Koji Academy). She inherits Nakaji’s koji making philosophy and approach which is traditional yet flexible.

 With aspiration of making koji as a global culture as well as contributing to boost community welfare with it, she is involved in a various forms of activities such as having a stall at farmer’s market, hosting online/offline workshops, participating educational events.

 She majored in chemistry in university and was trained as a computer engineer before embarking her career as a koji professional. Although the fields are very different, the influence of her backgrounds are clearly evident in her analytical approach in koji making (the glimpse of it is shown in her Instagram posts). She values both scientific evidence as well as sensory experience and is always searching for new subjects of trials and experiments, while carrying out research on new findings and journals. Her curious and inquisitive nature helped her to develop many connections with leading koji/brewing experts in Japan.

 Haruko is also a professional translator and translated “Koji for Life” into English

Haruko Uchishiba
stall @ stroud green market

Our activities

 In order to accomplish our aspiration and mission, we are actively involved in various form of activities, such as having a stall at Stroud Green farmers market and selling homemade koji condiments, participating in educational events and providing consultation to restaurants. 

 However, our main focus is hosting in-depth koji workshops both online and offline which spans over days to weeks. Our approach toward workshops are known to be very experiential and gains high-level of satisfaction. Whereas koji is an extremely powerful tool as a cooking element, it is something that you need to build up the experiences and engrain then into  your five sense. It is definitely not something you can learn by sitting, watching and listening. It also requires certain knowledge to make the most out of it. We design our workshops in a way you can gain confidence to deal with koji and optimise your setting on your own at the end of the class. We have a pride in providing such a course by deploying IT technology as best as we can.


Stroud Green farmers market - London, N4


Events - London Craft Week@Pantechnicon


Online workshops - Koji, Shoyu, Doburoku, Miso


  We supply following products in order to support your koji and miso making needs.

Koji for Life

Koji for Life

A bilingual book written by Nakaji, fully packed with valuable and indispensable information of koji making. It also gives deep insight about koji and Japanese history and culture as well as useful recipes. This book is absolutely must have for any koji lovers.

High quality Hishiroku koji starter

Koji spores

20g of quality koji starters to make 15 kg of koji from Hishiroku, Kyoto. The company has nearly 400 years of experience dealing with koji spore, established even before Leeuwenhoek, Dutch scientist, discovered the existence of microbe in 1674.

Miso Video

Two-parts series of miso making video accompanied by salt calculation Excel sheet. These comprehensive video covers not only the details of miso making and practical tips, but also many not so well known facts even among modern Japanese.

Koji packs

250g pack of organic koji grown on assorted substrates. These koji are carefully made in small batch with traditional Japanese koji-buta technique to fully ensure the balanced production of enzymes.

Miso kits

These are four types of traditional Japanese miso making kits which make 500-900g of organic miso (standard rice miso, Saikyo-sweet rice miso, sweet barley miso and very regional umami-rich red miso)
Instruction included.

The Koji Fermenteria's Koji Diary

Tsuyu, the rainy season in Japan, is translated as plum rain, because June is the time the plums ripen. The Japanese makes many kinds of plum preserves in this rainy season. I am introducing some plum preserves using koji.
Two new types of shoyu recently joined in my shoyu collection♥ lovely scallop flavoured shoyu & gluten free fava shoyu In this post, these two are analysed.
Commercially available rice koji might look all same in appearance but the enzyme balance could be very different! Are they up to your intended use!?
Growing koji on meat? Is it really different from simply coating meat with koji !? I have decided give it a go!
Bodaimoto is a 600 years-old excellent innovation of sake brewing method by Japanese ancestors. I am introducing how it is like and how to reproduce it in your kitchen.
I made very special miso today, which is a privilege as a koji grower. When you make your own koji, you can choose your own substrate and enzyme balance therefore you can design the taste and flavour of miso.

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Get in touch

Want to get in touch? We’d love to hear from you.

Latest News

11 May 2021

Will be back in Stroud Green

We will be back in Stroud Green. Koji natto, Pink shiokoji, Spicy soy dressing, Miso sesame dressing, Wild garlic pesto
11 May 2021

Koji for Life 6 copies remaining

Only 6 copies left in stock. Order now to avoid disappointment
11 May 2021

Koji starters restocked

Premium koji starters from Hishiroku restocked - 40 bags for rice and 20 bags for protein substrates

Koji Making - Online

The online koji making class takes place over the span of 10 days. The class structure is as follows.

Day 1       Guidance session (Zoom 1 hour):

What is koji?   Koji making overview Tools & equipment required

Day 7-9 Practical (Zoom & Facebook Live):

Day 7  Steam Inoculation Zoom 4 hours) Day 8  Mixing (Facebook Live) Day 9  Drying(Facebook Live)

Day 10     Wrap up (Zoom 1.5 hour)

        Review, Troubleshooting, QA         Koji application

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