*1.4.1 History of SCP*

In Germany during World War I and II, yeast was used to produce food for soldiers, prisoners, and the civilian population [51, 52]. Also, Russia and Japan used similar single-cell proteins for food [51]. Different feedstocks had been tested and used, also fossil-based ones, which gave a negative touch to the products in some peoples' eyes. Hence, in the year 1966, the term "single-cell protein" (SCP) was introduced by Carl L. Wilson, building upon prior successful productions of protein from fossil sources, to provide a more positive term than "petroprotein." In fact, in the Soviet Union, early attempts were made to obtain cost-effective protein from oil. "BVK" (belkovo-vitaminny kontsentrat = protein-vitamin concentrate) plants close to oil refineries in Kstovo (year 1973) and Kirishi (year 1974) were built [33]. Till 1989, eight such factories had been constructed by the Soviet Ministry of Microbiological Industry [33].

In Russia, the single-cell protein variants were called "Gaprin" (SCP from methane) [53], "Paprin" (SCP from paraffins), [54, 55] "Meprin" (SCP from methanol), and Eprin (SCP from ethanol). The total capacity was estimated at 1.5 million tons of SCP per year [56].

Work was pioneered by Alfred Champagnat [57, 58].

For petroleum-derived SCP, see [59–62].

Also in Western Europe, similar attempts were made. British ICI (Imperial Chemical Industries Ltd) succeeded in commercializing Pruteen™ single-cell protein. As feedstock, methanol was used, deploying *Methylophilus methylotrophus* in a 1500 m<sup>3</sup> airlift fermenter [63, 64]. That production was a major milestone in biotechnology [65]. It can be considered the foundation for mycoprotein Quorn™ [66, 67], which is made from a fungus (*Fusarium venenatum*) from sugar and sold on the order of several 10,000 tons/year today as a meat replacement.

The historic Pruteen™ plant was designed for an output of 50,000–75,000 metric tons/year. The investment was \$70 million (1979), and development costs had been \$20 million [68].

Scientific American [69] wrote in 1981*: "Beer, Wine, bread, and cheese have been made by microorganisms since Neolithic times. To them have been added spirits, yogurt, pickles, sauerkraut, Oriental fermented foods, and today single-cell protein."*

The BP (British Petrol) SCP process for "Toprina" is described in Ref. [70]. French activities from SCP from methane are reviewed in Ref. [71].

*Value-Added Products from Natural Gas Using Fermentation Processes: Products… DOI: http://dx.doi.org/10.5772/intechopen.104643*

German Hoechst/Uhde had developed Probion™ as a single-cell protein from *Methylomonas clarae* with 70% protein content [56]. A purified version, with 90% protein content with the nucleic acids and fats being removed, was intended for human consumption under the name Probion-S [56].

Liquipron™ (by Liquichimica from Italy) production is detailed in Ref. [72].

Another early, large single-cell protein project was Bioprotein™, which company Norferm (owned 50–50 by Statoil and Anglo-Norwegian pharmaceuticals group Nycomed Amersham [73], later DuPont) developed. Out of Norferm, the companies Calysta and UniBio developed. The Norferm SCP plant can be seen in **Figure 2**. Bioprotein™ was made from methane.

In the Norferm process, methane (from natural gas), oxygen, ammonia, and minerals were fermented. The concentration of the biomass was 20 g/L, and the temperature was 45°C in a continuous process. By centrifugation, the biomass was concentrated to 80–90 g/L in centrifuges and then further to 220 g/L by ultrafiltration. By a *"short intensive heat process, the cells are partially opened to improve the digestibility of the protein."* Spray drying is used to dry the biomass. The specific growth rate was 0.2/h, corresponding to biomass productivity of 4 kg/h/m3 [74].

These numbers are confirmed from additional sources; industrial production of SCP is feasible at an output of 4.0 kg biomass/m<sup>3</sup> reactor/h with an expected yield of 0.8 g biomass/g CH4 [75]. The process is shown in **Figure 3**.

The cooling requirement amounted to 62.3 MJ/kg of biomass, and the total volume of the loop reactor measured 300 m<sup>3</sup> . As a strain, *M. capsulatus* was used to yield the following product composition:


**Figure 2.** *The historic Norferm single-cell protein production facility at Tjeldbergodden, Norway. Source: [74].*

**Figure 3.**

*Process diagram of the single-cell protein process at Norferm. Source: [74].*

Norferm's BioProtein® (BP) SCP had been approved in the EU *"as a protein source in animal feeds since 1995, for fattening pigs (8%), calves (8%) and salmon (19-33%)"* [76].

**Table 9** provides an overview of several other commercially implemented SCP processes from the "golden age" of the industry around the year 1977 when also licensing options were available [78, 79]. An interesting retrospective view is provided by [80].

Another well-known SCP derived from n-alkanes (paraffins) was Fermosin™ [61]. **Table 10** gives additional projects (status 1977).

The overview above gives testimony of a fairly developed industry, which then disappeared again from the market. Fifty years ago, SCP succeeded technologically, but then failed economically, mainly due to cheap soy prices and increasing fossil fuel costs, as this quotation for the pertinent literature exemplifies:

*"By 1974, Shell announced plans for enlarged pilot plant facilities at Sittingbourne, and a development program in Amsterdam, with the ultimate goal of constructing a 100,000 ton/year plant. In the spring of 1976, however, Shell announced that it had stopped work on commercialization, and the expansion and development plans were "indefinitely postponed." The decision was said to be based on three factors the low price of soybeans and maize; the potential in large areas of the world for expanding existing sources of protein; and the difficulty of applying Shell's sophisticated process in* "underdeveloped countries" *[77]*.

So Shell bailed out of SCP within a short period of time, after prior heavy investments. That step cannot be considered unusual, compare to the press release from Dow in 2005 [81], when Dow stepped out of the bioplastics business *"due to slow sector maturation"* after having invested an estimated 750 million USD.

Four seminal books on SCP are [51, 82–84].

### *1.4.2 Use of SCP: Feed and food*

SCP has multiple possible applications, both in the feed sector and in the food sector [33, 48, 85], see **Table 11**:


*Value-Added Products from Natural Gas Using Fermentation Processes: Products… DOI: http://dx.doi.org/10.5772/intechopen.104643*
