Aims:  Application of Halobacterium sp. SP1(1) for the acceleration of fish sauce fermentation. Methods and Results:  Traditional fish sauce fermentation was mimicked using Halobacterium sp. SP1(1) as starter culture. Protease activity, peptide release and α‐amino content (parameters used to monitor the progress of the fermentation) were high at day 10 in tests and day 20 in un‐inoculated controls. The total protein and nitrogen contents were also high in tests compared with controls. The amino acid profile observed at the end of fermentation in experimental samples, when compared with the commercial sauce preparation, was found to be better with respect to flavour and aroma contributing amino acids as well as essential amino acid lysine. Microflora analysis of the final fish sauce revealed the absence of any nonhalophilic or halotolerant micro‐organisms. The protease‐producing halophilic isolates obtained from the fish sauce of eviscerated and uneviscerated controls were identified as Halobacterium sp. F1 and F2, respectively, by 16S rDNA sequence analysis. Conclusions:  Exogenous augmentation of Halobacterium sp. SP1(1) accelerated the fish sauce fermentation process with an additive effect on the existing natural microflora present in the fish during fermentation. Halobacterium sp SP1(1), therefore, can be used as an important starter culture for accelerating the fish fermentation process, which is attributed to its extracellular protease. Significance and Impact of the Study:  The present study is the first report on use of Halobacterium species as a starter culture for accelerating fish sauce fermentation. Use of halobacterial starter cultures may revolutionize the process in fish sauce industries by reducing the fermentation time and making the process more economical with improved nutritive value of product.

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Halophilic archaea belonging to three different genera- Halobacterium, Haloarcula and Haloferax, were isolated from Kandla salt pans. The isolates had an optimum requirement of 25% NaCl for growth. Increase in organic solvent tolerance of isolates was observed at higher NaCl concentrations. Among the three isolates Halobacterium sp. SP1(1) was found to be more tolerant than Haloarcula sp. SP2(2) and Haloferax sp. SP1(2a). The extracellular protease of Halobacterium sp. SP1(1) showed higher solvent tolerance compared to the organism itself. The enzyme was highly tolerant to toluene, xylene, n-decane, n-dodecane and n-undecane, majority of which are frequently used in paints. These findings may help in understanding the mechanism of organic solvent tolerance in halophilic archaea and their application in antifouling coatings. Also, best to our knowledge the present study is the first report on organic solvent tolerance of haloarchaeal extracellular protease.

Aims:  Optimization of medium components for extracellular protease production by Halobacterium sp. SP1(1) using statistical approach. Methods and Results:  The significant factors influencing the protease production as screened by Plackett–Burman method were identified as soybean flour and FeCl3. Response surface methodology such as central composite design was applied for further optimization studies. The concentrations of medium components for higher protease production as optimized using this approach were (g l−1): NaCl, 250; KCl, 2; MgSO4, 10; tri‐Na‐citrate, 1·5; soybean flour, 10 and FeCl3, 0·16. This statistical optimization approach led to production of 69·44 ± 0·811 U ml−1 of protease. Conclusions:  Soybean flour and FeCl3 were identified as important factors controlling the production of extracellular protease by Halobacterium sp. SP1(1). The statistical approach was found to be very effective in optimizing the medium components in manageable number of experimental runs with overall 3·9‐fold increase in extracellular protease production. Significance and Impact of the Study:  The present study is the first report on statistical optimization of medium components for production of haloarchaeal protease. The study also explored the possibility of using extracellular protease produced by Halobacterium sp. SP1(1) for various applications like antifouling coatings and fish sauce preparation using cheaper raw material.